Head-mounted virtual image display device having switching means enabling user to select eye to view image

ABSTRACT

A head-mounted display device for enlarging an image formed by an image display element as a virtual image. The head-mounted display device according to this invention comprises a virtual image forming optical system (3) including an image display element (9) and a lens (11) for enlarging an image formed by the image display element (9); a device main body (1) that houses the image forming optical means (3); and a switching means mounted in the device main body (1) for holding the virtual image forming optical system (3) in such a way that the system (3) can be moved in the direction of the width of the eye and placing the virtual image forming optical system (3) in front of one of the user&#39;s eyes. The image display element (9) and the lens (11) are disposed so that the optical axis of the virtual image forming optical system (3) approximately aligns with the user&#39;s line of sight taken while he or she is looking horizontally. The switching means enables the user to easily select the eye to view the virtual image. Therefore, this invention provides high universality and shareability, and enables the user to freely switch the eye to view the virtual image.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a head-mounted image display devicethat enlarges an image formed by an image display element and thatdisplays it as a virtual image, and in particular, to such a device thatis preferably used as a monitor for a data display in a personalcomputer or a word processor (hereinafter referred to as PC monitor).

2. Description of the Prior Art

Head-mounted display devices have been proposed to meet demand forincreased portability of image and data displays. One typical example isa portable head-mounted display device described in detail in U.S. Pat.No. 5,162,828, which is commercially available under the name of"Virtual Vision SPORT". This device is configured to enlarge an imageformed by a liquid crystal display element and to display it as avirtual image around the user's field of view. This device, however, ismainly used as an image display, and is not appropriate as a PC monitorfor various reasons stated below.

A known head-mounted display device for displaying data is aspectacle-like head-mounted display device described in PublishedUnexamined Patent Application No. 5-100,192.

In general, a data display employing such a head-mounted display deviceis used with an input means such as a keyboard located near the user'shands, and the device is mounted on the user's head to enable the userto monitor input information above the input means. Materials andmanuscripts required to input information must sometimes be placedaround the input means, so the field of view must be available below thehead-mounted display device in order to view the input means and thesematerials. The above head-mounted display device (U.S. Pat. No.5,162,828), however, forms virtual images around the user's field ofview, as described above, and in particular, commercially available suchdevices are configured to form virtual images below the user's field ofview. The field of view for the virtual image thus overlaps the field ofview for the input means, materials or manuscripts. These displaydevices are significantly inappropriate as PC monitors. In addition,continuing such an operation often results in a fatigue of the usercaused by a continuous strain on the muscle responsible for rotating theeyeballs. In addition, the commercially available display devices forcethe user to look with the dominant eye, and the applicant's experimentdescribed below indicates that this is also one of the reasons for thefatigue. Furthermore, in these devises, a partially transparent shadingplate (a visor) defines the field of view for the external sight and allthe fields of view are obtained through this plate. Thus, if such adevice is used as a PC monitor, for example, the transmittance ofextraneous light through the partially transparent shading plateobtained when the input means is viewed is the same as the transmittanceof extraneous light seen by the other eye (the eye that does not see thevirtual image) when the virtual image is viewed; the applicant'sexperiment also indicates that this is also one of the reasons for thefatigue.

To partially solve the above problem, the latter head-mounted displaydevice (Published Unexamined Patent Application No. 5-100192) wasproposed. This device includes a partially transparent shading platethat enables the user to view information displayed on a data display,as a virtual image in front of the user and to see an input means suchas a keyboard below the device. This display device, however, is of whatis called a binocular type in which both eyes view respective imagesfrom two liquid crystal display elements, and thus brings about a largeweight, large costs, and a complicated structure and fails to providehigh portability. Accordingly, this device does not meet the basicrequirements of PC monitors. In addition, since it requires a binocularfusion when the virtual image is viewed, repetitive and alternativeviewing of the virtual image and the input means results in a fatigue.Furthermore, this display device is unavoidably subject to thedifference in brightness between the right and left liquid crystaldisplay elements and the difference in image quality such as colors, andthis is also one of the reasons for the fatigue. The front field of viewis not sufficiently provided while this device is in use, resulting in asense of oppression and low safety. As a result, the field of view isnarrow except for the virtual image, and the user is hindered fromperforming operations smoothly while viewing materials or manuscripts.Furthermore, said invention pays no attention to the difference betweenthe brightness of the monitor and the brightness on the input means.This causes the pupil to dilate or contract during repetitive andalternative viewing of the virtual image and the input means, being alsoone of the reasons for the fatigue.

BRIEF SUMMARY OF THE INVENTION

It is a primary objective of this invention to provide a head-mounteddisplay device that provides high visibility and that reduces the user'sfatigue.

It is another objective of this invention to provide a head-mounteddisplay device that provides high workability and safety.

It is yet another objective of this invention to provide a head-mounteddisplay device that functions as an ideal PC monitor that has a smallweight and size, a simple structure, and high portability and thatrequires small costs.

A head-mounted display device according to a first aspect of thisinvention comprises a virtual image forming optical system including animage display element and an enlarging optical means for enlarging animage formed by the image display element as a virtual image; a devicemain body that houses the virtual image forming optical system; and aswitching means mounted in the device main body for holding the virtualimage forming optical system in such a way that the system can be movedin the direction of the width of user's eyes and placing the virtualimage forming optical system in front of one of the user's eyes. Theimage display element and the enlarging optical means are disposed sothat the optical axis of the virtual image forming optical systemapproximately aligns with the user's line of sight taken while he or sheis looking horizontally.

In the first aspect of this invention, since the virtual image formingoptical system is located in front of one of the user's eyes, and theoptical axis formed by an virtual image and the user's eyesapproximately aligns with the user's line of sight taken while he or sheis looking horizontally, the user can view the virtual image in front ofone of his or her eyes (for example, the antidominant eye). Thismaximizes the field of view for the eye that need not see the virtualimage as well as that field of view for the eye to see the virtual imagewhich is located below the field of view for the virtual image. As aresult, this device enables the user to fully view an input means suchas a keyboard and materials or manuscripts, and is suitable as a PCmonitor and very safe. It reduces the user's fatigue because it onlyrequires the user to look in the horizontal direction that is the mostnatural direction of the line of sight. Furthermore, since this deviceis of a monocular type, the fatigue of the eyes is relieved compared tobinocular type display devices with which the user's eyes are likely tobe strained due to an binocular fusion or the difference between theright and left liquid crystal display elements in image quality. It alsohas a smaller weight and size, a simpler structure, and higherportability than binocular type display devices, and requires smallercosts.

The switching means enables the user to simply select the eye to see thevirtual image, thereby providing high universality and shareability andenabling the user to freely switch the eye to see the virtual image.

The fatigue can be reduced even in a long time use by setting the anglein the horizontal direction between the optical axis formed by thevirtual image and the user's eyes and a line perpendicular to the user'sface, at -1° to +5°, desirably, 0° to 1° when the convergent directionis assumed to be positive, because, in this case, the virtual image isseen in the direction in which the user can see the image most easilywith one eye.

According to a second aspect of this invention, in the display device inaccordance with the first aspect, the switching means comprises a shaftthat is retained so as to rotate without affecting the device main body,that extends approximately in the direction of the width of the user'seyes, that is shaped like a screw, and that has the virtual imageforming optical system spirally fitted thereto.

In the second aspect of this invention, the position of the virtualimage forming optical system can be simply switched by rotating theswitching means retained so as to rotate without affecting the devicemain body to move rightward or leftward the virtual image formingoptical system spirally fitted to the screw of the switching means.Since the virtual image forming optical system is moved in the directionof the width of the user's eyes, the switching means also enables thewidth of the eyes to be adjusted. This prevents the unnatural movementof the eyeballs to eliminate strains on the eyes caused by themisalignment of the device with the width of the user's eyes, therebysimplifying adjustment mechanisms required for this purpose.

According to a third aspect of this invention, the display device inaccordance with the first aspect further has a partially transparentshading plate provided in front of the eye that need not see an imageenlarged by the enlarging optical means and having a transmittance ofless than 1.

In the third aspect of this invention, since the partially transparentshading plate with a transmittance of less than 1 is disposed in frontof the eye that need not see the virtual image, the front and downwardfields of view can be maximized while the device is in use withoutfailing to perceive the virtual image, thereby improving workability andsafety. Workability and safety can further be improved by preferablyusing a partially transparent shading plate of a size equal to or largerthan that of the field of view for the virtual image and by optimizingthe transmittance of the shading plate. The optimal solution for thetransmittance that minimizes the fatigue has been confirmed by theexperiment described below.

According to a fourth aspect of this invention, the display device inaccordance with the third aspect further has a control means forvariably controlling the transmittance of the partially transparentshading plate according to the surrounding illuminance.

In the fourth aspect of this invention, the transmittance of thepartially transparent shading plate is variably controlled according tothe surrounding illuminance so as to optimize the transmittance. Thisimproves workability and safety and minimizes the user's fatigue. Thepartially transparent shading plate comprises, for example, a polarizingelement, a liquid crystal display element, or film-type liquid crystaldisplay element comprised of a liquid crystal filled between deformableresins.

According to a fifth aspect of this invention, in the display device inaccordance with the fourth aspect, that transmittance of the partiallytransparent shading plate is controlled so as to be 3% or less.

According to a sixth aspect of this invention, in the display device inaccordance with the fourth aspect, the transmittance of the partiallytransparent shading plate is controlled so as to increase when thesurrounding illuminance is 1001× or less.

In the fifth or sixth aspect of this invention, the transmittance of thepartially transparent shading plate is optimized because it iscontrolled so as to be 3% or less and to increase when the surroundingilluminance is 1001× or less.

According to a seventh aspect of this invention, the display device inaccordance with the third aspect further has a partially transparentshading plate with a transmittance of less than 1 which is provided in aspace opposite to the user relative to the virtual image forming opticalsystem to cover at least the overall movement area of the virtual imageforming optical system.

In the seventh aspect of this invention, the partially transparentshading plate with a transmittance of less than 1 is located all overthe image formation area in the movement area of the virtual imageforming optical system, so the apparent contrast of the virtual imageincreases to improve visibility. In addition, the need to remove andinstall the partially transparent shading plate in switching the eye tosee the virtual image is eliminated, thereby enabling the user to easilycarry out the switching of the eye to see the virtual image and theadjustment of the eye width.

A compact head-mounted display device can be implemented by preferablydisposing the partially transparent shading plate so as to incline about45° relative to the vertical direction. Furthermore, applyinganti-reflection processing to the user's side of the partiallytransparent shading plate can prevent reflection from the opposite sideas well as the surrounding light from affecting the user's side of theshading plate, thereby enabling the implementation of a head-mounteddisplay device with high visibility.

According to an eighth aspect of this invention, the display device inaccordance with the first aspect further has a control means forproviding variable control based on the surrounding brightness under thedevice main body and near the user's hands while the device is in use.

In the eighth aspect of this invention, the relationship between thebrightness of the virtual image forming optical system and thebrightness near the user's hands are optimized to reduce the differenceof the brightness perceived by the user alternatively viewing thevirtual image and looking near his or her hands, thereby minimizing hisor her fatigue. This has also been confirmed by the experiment describedbelow. For example, by disposing an illuminance (brightness) detectionmeans below the device main body so as to sequentially detect theilluminance in front of the device and the brightness near the user'shands, the results of detection can be fed back to optimize thetransmittance of the partially transparent shading plate and thebrightness of the virtual image forming optical system, thereby enablingthe automatic optimization of the transmittance of the shading plateand/or the brightness of the virtual image forming optical system. As aresult, the device is always adjusted to its optimal conditionsaccording to the user's operating conditions.

According to a ninth aspect of this invention, in the display device inaccordance with the eighth aspect, the brightness of the virtual imageforming optical system is controlled so as to be equal to thesurrounding brightness.

In the ninth aspect of this invention, the brightness of the virtualimage forming optical system is controlled so as to be equal to thesurrounding brightness, so the difference of the brightness perceived bythe user in alternatively checking the virtual image and viewing thesurroundings is eliminated to minimize the user's fatigue.

According to a tenth aspect of this invention, in the display device inaccordance with the eighth aspect, the brightness of the virtual imageforming optical system is controlled so as to be approximately inproportion to the surrounding brightness.

In the tenth aspect of this invention, the brightness of the virtualimage forming optical system is controlled so as to be approximately inproportion to the surrounding brightness, so the difference of thebrightness perceived by the user in alternatively checking the virtualimage and looking to the surroundings, for example, near his or herhands is eliminated to minimize the user's fatigue.

According to an eleventh aspect of this invention, the display device inaccordance with the first aspect further has a diopter adjustment meansfor adjusting the position in which an enlarged virtual image from theimage display element is formed.

In the eleventh aspect of this invention, if the head-mounted displaydevice is used with a keyboard, before starting operations, theswitching means is used to place an image formed by the image displayelement in a position in which the image does not two-dimensionallyoverlap the keyboard. The diopter adjustment means is also used to setthe distance to the virtual image and the distance to the keyboard atthe same value. This reduces the amount of the movement of the user'sfield of view between the image and the keyboard as well as the amountof accommodetion for the eyes, thereby enabling the provision of ahead-mounted display device that provides high workability and thatreduces a sense of fatigue and uncomfortableness.

According to a twelfth aspect of this invention, the display device inaccordance with the eleventh aspect further has a diopter adjustmentcontrol on both sides of the virtual image forming optical system.

In the twelfth aspect of this invention, since the diopter adjustmentcontrol provided on both sides of the virtual image forming opticalsystem can be used to adjust diopter, diopter can be adjusted easilywhether the virtual image forming optical system is located in front ofthe right or left eye.

According to a thirteenth aspect of this invention, in the displaydevice in accordance with the eleventh aspect, the conditions of thediopter adjustment means are shown so as to correspond to the positionin which an virtual image is formed.

In the thirteenth aspect of this invention, since the conditions of thediopter adjustment means are shown so as to correspond to the positionin which an enlarged virtual image is formed, the distance from theuser's eyes to the keyboard and the distance from the user's eyes to thevirtual image can be set at the same value easily. Such a settingreduces the user's fatigue during operations.

According to a fourteenth aspect of this invention, in the displaydevice in accordance with the eleventh aspect, the position in which anenlarged virtual image is formed can be set stepwise at one of aplurality of positions using the diopter adjustment means.

In the fourteenth aspect of this invention, if, for example, theposition in which a virtual image is formed is set stepwise at one of aplurality of positions so as to correspond to the range of the distancebetween the operator's eyes and the keyboard during a VDT operation, theoperator can usually adjust diopter quickly and appropriately, and evenwhen changing his or her posture during the operation, also carry outadequate adjustment using a fixed position as a reference with thehead-mounted display device mounted on his or her head. In addition, ifthis position is set stepwise at a distance 50, 60, or 100 cm from theuser's eyes, an image can be reliably formed in a position in which theVDT operator usually suffers a reduced fatigue.

According to a fifteenth aspect of this invention, the display device inaccordance with the first aspect further has a holding means attached tothe device main body via a rotatable hinge section for holding thedevice main body to the user's head.

In the fifteenth aspect of this invention, rotating the device main bodyaround the hinge section enables the angle of depression to be adjustedto prevent the user from taking an unnatural line of sight, therebyreducing strains on the user's eyes. This also enables the correction ofthe vertical inclination of the holding means caused by the differencein the user's physique to prevent the positional deviation of the user'seyes from the virtual image forming optical system, thereby reducingstrains on the user's eyes. The device main body can be folded towardthe holding section around the hinge section to save space.

According to a sixteenth aspect of this invention, the display device inaccordance with the first aspect further has a drive circuit fixed anddisposed outside the movement space in the transverse movement area ofthe virtual image forming optical system for driving the image displayelement and a flexible printed circuit interposed between the imagedisplay element and the drive circuit for connecting them together.

In the sixteenth aspect of this invention, the drive circuit is fixedand disposed outside the movement space in the transverse movement areaof the virtual image forming optical system, and the image displayelement and the drive circuit are connected together by the flexibleprinted circuit, the flexibility of the cable between the virtual imageforming optical system and the device main body which is required whenthe optical system moves in response to the switching of the eye to seethe virtual image can be improved to thereby enable the optical systemto move reliably and smoothly. In addition, the virtual image formingoptical system can be moved within a cable housing space with a smallheight, resulting in a reduced size of the overall device.

According to a seventeenth aspect of this invention, in the displaydevice in accordance with the sixteenth aspect, the drive circuit has adetachable part disposed approximately in parallel with the direction ofthe width of the user's eyes for allowing the flexible printed circuitto be attached to or removed from the drive circuit in the directionthat aligns with the lateral moving direction of the virtual imageforming optical system, and further has a guide means disposed betweenthe detachable part and the image display element for guiding theflexible printed circuit approximately perpendicular to the lateralmoving direction of the virtual image forming optical system.

In the seventeenth aspect of this invention, the drive circuit is placedflatly outside the movement space in the lateral movement area of thevirtual image forming optical system approximately in parallel with thedirection of the width of the user's eyes, so the heat release effect ofthe drive circuit is enhanced to thereby improve the reliability of thecircuit. In addition, placing the drive circuit flatly serves toincrease the packaging area of the circuit substrate, thereby reducingthe height of the circuit housing space to reduce the size of theoverall device. Furthermore, stress on the detachable part and theflexible printed circuit is minimized because the flexible printedcircuit can be attached to or removed from the drive circuit in thedirection that aligns with the lateral moving direction of the virtualimage forming optical system, and the guide means is disposed betweenthe detachable part and the image display element for guiding theflexible printed circuit approximately perpendicular to the lateralmoving direction of the virtual image forming optical system. Thus, theaccidental removal of flexible printed circuit is prevented, therebyenabling the virtual image forming optical system to move transverselysmoothly.

According to an eighteenth aspect of this invention, the display devicein accordance with the first aspect further has a center determinationsupport means provided in the approximate center of the device main bodyand used to determine whether or not the user's center line aligns withthe center of the device main body while the device is in use.

In the eighteenth aspect of this invention, the center determinationsupport means is provided in the approximate center of the device mainbody to enable the center to be always confirmed easily whether thevirtual image forming optical system is located in front of the user'sright or left eye. This constitution prevents the disalignment of theoptical axis of the virtual image forming optical system with the user'sline of sight which is caused by the misplacement of the device mainbody.

In the display device in accordance with the eighteenth aspect of thisinvention, by preferably disposing the partially transparent shadingplate outside the virtual image forming optical system relative to theuser so as to cover the fields of view of both eyes and providing alocation mark at the center of the shading plate as the centerdetermination support means, the user can use the location mark todetermine the center despite defocusing, thereby suppressing thepositional deviation of the display device regardless of the transversemovement of the virtual image forming optical system. Consequently, thepositional deviation of the display device can be prevented withoutaffecting the transverse movement of the virtual image forming opticalsystem, thereby minimizing a fatigue caused by such a deviation.

According to a nineteenth aspect of this invention, the display devicein accordance with the first aspect further has an antidominant eyedetermination support means provided in the approximate center of thedevice main body and used to determine the antidominant eye.

In the nineteenth aspect of this invention, by providing theantidominant eye determination support means in the approximate centerof the width of the user's eyes in the device main body, the relativepositions of a virtual image and an image of the antidominant eyedetermination support means which are determined by both eyes can becompared to the same relative positions which are determined by only oneeye to see the virtual image, thereby enabling the easy determination ofthe eye to see the virtual image (the antidominant eye). That is, theapplicant's experiment indicates that allowing the antidominant eye tosee the virtual image a little more reduces the fatigue of the eyescompared to the use of the dominant eye. The antidominant eyedetermination support means can thus be used to determine which eye hasa poorer eyesight. The virtual image forming optical system can then bemoved so as to stand in front of the antidominant eye to allow this eyeto view the virtual image.

In the device in accordance with the nineteenth aspect of thisinvention, by preferably disposing the partially transparent shadingplate outside the virtual image forming optical system so as to coverthe fields of view of both eyes and providing the antidominant eyedetermination support means at the approximate center of the width ofthe user's eye, the operator can easily determine the eye to see thevirtual image, with the head-mounted display device mounted on his orher head. In this operation, the antidominant eye which is used to seethe virtual image can be determined easily by comparing the relativepositions of a virtual image or an external sight information and animage of the antidominant eye determination support means which aredetermined by both eyes, the same relative positions determined by onlyone of the eyes, and the same relative positions determined by the othereye, thereby preventing the eye to see the virtual image from beingmistakenly selected. This also leads to the reduced fatigue of theoperator's eyes.

According to a twentieth aspect of this invention, in a head-mounteddisplay device in accordance with the first aspect, the virtual imageforming optical system has a partially transparent mirror and furtherhas a pupil detection means disposed in the position corresponding tothe optical axis of the virtual image forming optical system fordetecting the position of the user's pupil via the partially transparentmirror, and a means for informing the user of the misalignment of thevirtual image forming optical system with the pupil in response to theoutput of the pupil detection means.

In the twentieth aspect of this invention, since the partiallytransparent mirror is provided in the virtual image forming opticalsystem, and the pupil detection means is disposed via the partiallytransparent mirror in the position corresponding to the optical axis ofthe virtual image forming optical system, the position of the user'spupil can be detected without providing a larger device main body. Inaddition, the position of the user's pupil can be detected and the usercan be informed of the misalignment of it with the virtual image formingoptical system, if any, so the virtual image forming optical system canbe positioned easily and accurately in front of the user's pupil. Thisreduces the fatigue of the eyes caused by the misplacement of thedevice.

Furthermore, if the means for informing the user of the misalignment ofthe user's pupil with the virtual image forming optical system employs,for example, sounds, the constitution of the display device issimplified, and the user can notice the misalignment more easily.

If the means for informing the user of the misalignment of the user'spupil with the virtual image forming optical system allows the imageformed by the image display element to disappear for this purpose,misuse due to the misalignment can be prevented, and the user can noticethe misuse without affecting surrounding people. As a result, strains onthe eyes and uncomfortableness can be reduced, and the power of thedevice can be reduced. If this means displays overlapping images forthis purpose, misuse due to the misalignment of the user's pupil withthe virtual image forming optical system can be prevented, and the usercan notice the misuse without affecting surrounding people, even undernoisy conditions, or even if he or she is hard of hearing. Consequently,strains on the eyes and uncomfortableness can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a model perspective view showing a first embodiment of thisinvention;

FIG. 2 is a model side view showing the first embodiment;

FIG. 3 is a model plan describing the position of a partiallytransparent shading plate according to the first embodiment;

FIG. 4 is a model drawing describing the size of the partiallytransparent shading plate according to the first embodiment;

FIG. 5 shows the results of experiment on the relationship between thesurrounding illuminance and the transmittance of the partiallytransparent shading plate;

FIG. 6 shows the results of experiment on the relationship between thesurrounding illuminance and the brightness of the transmittance of avirtual image forming optical system;

FIG. 7 describes the virtual image forming optical system in the firstembodiment and an input means located below the optical system;

FIG. 8 shows the relationship between the distance to a virtual imagewhen this image is viewed and the distances to the virtual image and aninput means when this input means is viewed;

FIG. 9 describes the horizontal position in which a virtual image isformed;

FIGS. 10A describes a circuit for controlling the transmittance of thepartially transparent optical system, and FIG. 10B is a timing chartshowing a waveform obtained while the circuit is operating;

FIG. 11 is a circuit diagram showing an embodiment of brightness controlby the virtual image forming optical system;

FIG. 12 is a model front view showing a second embodiment of thisinvention;

FIG. 13 is a model side view showing the second embodiment;

FIG. 14 is a model front view showing a third embodiment of thisinvention;

FIG. 15 is a model side view showing the third embodiment;

FIG. 16A and 16B are a top view and a side view, respectively, showingthe structure of a slider representing the third embodiment;

FIG. 17 describes the operation of a supporting point representing thethird embodiment;

FIG. 18 is a model front view showing a fourth embodiment of thisinvention;

FIG. 19 is a model side view showing the fourth embodiment;

FIG. 20 is an enlarged view of an optical system representing the fourthembodiment;

FIG. 21 is a model perspective view of the optical system in FIG. 20;

FIG. 22 is a model front view showing a variation of the fourthembodiment;

FIG. 23 is a model side view of the variation in FIG. 22;

FIG. 24 is a model front view showing a fifth embodiment of thisinvention;

FIG. 25 is a model side view showing the fifth embodiment;

FIGS. 26A, 26B, and 26C show a relative positional relationshipdescribing a method for determining the antidominant eye according tothe fifth embodiment;

FIG. 27 is a model front view showing a sixth embodiment of thisinvention;

FIG. 28 is a model side view showing the sixth embodiment;

FIGS. 29A and 29B show a relative positional relationship describing amethod for determining the antidominant eye in the sixth embodiment;

FIG. 30 is a model side view showing the sixth embodiment;

FIG. 31A and 31B describe the movement of a virtual image formingoptical system in the direction of the width of the eye according to aseventh embodiment of this invention;

FIG. 32 is a model front view showing an eighth embodiment of thisinvention;

FIG. 33 is a model side view showing the eighth embodiment;

FIG. 34 is a model front view describing a shading means according tothe eighth embodiment;

FIG. 35 is a flowchart describing a method for mounting the displaydevice on the user's head according to the embodiments of thisinvention;

FIG. 36 is a flowchart describing a method for determining theantidominant eye according to the fifth embodiment;

FIG. 37 is a flowchart describing a method for determining theantidominant eye according to the sixth and seventh embodiments;

FIG. 38 is a flowchart describing a method for determining theantidominant eye according to the eighth embodiment;

FIG. 39 is a model front view showing a tenth embodiment of thisinvention;

FIG. 40 is a model side view showing the tenth embodiment;

FIG. 41 is a model side view showing an eleventh embodiment of thisinvention;

FIG. 42 is a model front view showing a twelfth embodiment;

FIG. 43 is a partially enlarged view showing mechanisms around a knob inthe above embodiment;

FIG. 44 is an enlarged view of an optical system representing afourteenth embodiment of this invention;

FIG. 45 is an enlarged view of an optical system representing afifteenth embodiment of this invention;

FIG. 46 is an enlarged view of an optical system representing asixteenth embodiment of this invention;

FIG. 47 is a model top view showing a seventeenth embodiment of thisinvention;

FIG. 48 is a model side view showing the seventeenth embodiment;

FIG. 49 is a model top view showing an eighteenth embodiment of thisinvention;

FIG. 50 is a model side view showing the eighteenth embodiment;

FIG. 51 schematically describes the configuration of a virtual imageforming optical system representing a nineteenth embodiment of thisinvention;

FIG. 52 schematically shows a method for using the virtual image formingoptical system in FIG. 51;

FIG. 53 is a perspective view of a head-mounted display devicerepresenting the nineteenth embodiment;

FIG. 54 is a schematic cross section of a monitor section mountingstructure-according to the nineteenth embodiment;

FIG. 55 schematically describes the constitution of a virtual imageforming optical system showing a twentieth embodiment of this invention;

FIG. 56 is a perspective view of a head-mounted display devicerepresenting the twentieth embodiment;

FIG. 57 describes the layout of an image and a keyboard according to thetwentieth embodiment;

FIG. 58 is a perspective view describing a method for adjusting ahead-mounted display device representing a twenty first embodiment ofthis invention;

FIG. 59 is a perspective view describing a method for adjusting thehead-mounted display device representing the twenty first embodiment ofthis invention;

FIG. 60 is a perspective view showing, a window representing the twentyfirst embodiment;

FIG. 61 describes the arrangement of the components of a virtual imageforming optical system in a head-mounted display device according to atwenty second embodiment of this invention; and

FIGS. 62A and 62B describe a diopter adjustment mechanism according tothe twenty second embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1)

FIGS. 1 and 2 are model drawings showing a first embodiment indicatingthe principle of the operation of this invention. FIG. 1 is aperspective, and FIG. 2 is a side view. Both figures also show theposition of an internal optical system.

In FIGS. 1 and 2, a device main body 1 has a vertical image formingoptical system 3 in its front corresponding to one of the eyes of a user2 and a partially transparent shading plate 4 in front of the other eye.The virtual image forming optical system 3 and the partially transparentshading plate 4 are connected together near the center of the user'sface via the structure of the device, and connected to a right and lefttemples 5 foldably retained by a hinge 6, via the structure of thedevice extending rightward from the optical system and leftward from theshading plate. The device main body 1 is approximately shaped likespectacles, and supported by the user's ears and nose or the user'stemples and nose so as to be retained on the user's head.

The virtual image forming optical system 3 comprises an image displayelement 9 consisting of a liquid crystal panel 7 and a back light 8 forirradiating the panel with light from behind, a reflection mirror 10,and a lens 11 that acts as an enlarging optical means. An image lightformed and output by the image display element 9 has its path changed bythe reflection mirror 10 and formed as an image within the user's eye 12by the lens 11. In this case, if the image formation plane of the imagedisplay element 9 is located beyond the object-side focus of the lens 11and near the lens 11 and the eye 12 is located near the image-side focusof the lens 11, then the image formation function of the lens 11 causesan enlarged virtual image 14 of screen information to be seen on theextension of the optical axis 13 of the virtual image forming opticalsystem 3.

In these figures, the optical axis 13 of the virtual image formingoptical system 3 is formed by a virtual image 14 and the user's eye 12,and approximately aligns with the user's line of sight when he or shelooks to the horizontal direction, as is apparent from the side viewshown in FIG. 2. In addition, the applicant's investigation indicatesthat if this device is used as a PC monitor, the horizontal angle ofview of the virtual image is desirably 30° to 40°, which corresponds toa vertical angle of view φ of 23° to 30°. As shown in FIG. 2, asufficient field of view for the external sight (the hatched area in thefigure) is available below the field of view for the virtual imagedefined by the vertical angle of view φ in the vertical direction,although precisely speaking, this field of view is somewhat reduced bythe virtual image forming optical system 3. According to thisembodiment, the virtual image forming optical system 3 is disposed infront of only one eye, and the front field of view for the other eye isinherently available, so in operation, an input means such as a keyboardand materials or manuscripts can be sufficiently viewed. This displaydevice is thus suitable as a PC monitor and very safe.

In addition, the user's fatigue is reduced because the user can continueviewing the virtual image in the horizontal direction that is the mostnatural direction of the line of sight. Furthermore, since this deviceis of a monocular type, the fatigue of the eyes is relieved compared tobinocular type display devices with which the user's eyes are likely tobe strained due to a binocular fusion or the difference in image qualitybetween the right and left liquid crystal display elements. This devicealso has a smaller weight and size, a simpler structure, and higherportability than binocular type devices, and requires smaller costs.

Table 1 shows the results of subjective evaluation in which the fatigueof the dominant eye was compared to that of the antidominant eye(hereinafter called the "other eye") after each eye had been allowed tosee a virtual image. Five subjects were used, and the virtual imageforming optical system 3 shown in the first embodiment (FIGS. 1 and 2)was set in front of the dominant eye or the other eye to have themcontinue inputting data from a subject document for one hour. For boththe dominant eye and the other eye, the partially transparent shadingplate 4 was set in front of the eye that need not see the virtual imagein such a way that the shading plate would provide full or partialshading. The results are also shown in the table. The degree of thefatigue was classified into four levels: A: no sense of fatigue; B:somewhat fatigued; C: substantially fatigued; D: painfully fatigued.White circles represent the number of subjects, while black circlesrepresent the number of subjects who could not get over their fatigueafter operation.

Table 1 indicates that compared to the dominant eye, allowing the othereye to view the virtual image reduces the fatigue regardless of form ofthe partially transparent shading plate 4. Allowing the other eye toview the virtual image not only serves to relieve the fatigue but alsoenables the implementation of a PC monitor that reduces strains on theoperator's eyes.

                  TABLE 1                                                         ______________________________________                                                     Fatigue                                                          Form         A         B        C     D                                       ______________________________________                                        Other eye, full                                                                            ∘                                                                           ∘∘                                               ∘                                 transmission                                                                  Other eye, partial                                                                         ∘                                                                           ∘∘∘                transmission                                                                  Other eye, shading                                                                         ∘                                                                           ∘∘                                                                               Dominant eye, full     ∘                                                            ∘                                                                                   transmission                                                                  Dominant eye,                                                                              ∘                                                                           ∘                                                                                                                                                            partial                                                                       transmission                                                                  Dominant eye,          ∘                                                                                                              5                               shading                                                                       ______________________________________                                    

As described above, Table 1 shows the relationship between the degree offatigue and the transmittance of the partially transparent shading plate4. This table indicates that when the other eye is allowed to view thevirtual image, the sense of fatigue is weakest with partialtransmission, second weakest with shading, and strongest with fulltransmission, although this is not clear in the case of the dominanteye. In particular, it is found that no fatigue is virtually sensed whenthe other eye is allowed to view the virtual image while simultaneouslythe partially transparent shading plate set to provide partialtransmission is placed in front of the dominant eye. The inventorassumes that the reasons are as follows.

First, information from the dominant eye is dominant in the sense ofsight. This is because the ophthalmic nerve from the dominant eyeincluding the associated cerebral nerve has a higher sensitivity. Thefatigue can thus be reduced by displaying on the other eye a virtualimage with a high stimulus.

Second, the partially transparent shading plate set to provide partialtransmission prevents a decrease in the contrast of the virtual imagecaused by the overlapping of the virtual image and the external sight toenable the virtual image to be seen clearly, thereby reducing thefatigue.

Third, when the virtual image and the input means such as a keyboard arerepetitively and alternatively viewed, the use of the partiallytransparent shading plate set to provide partial transmission causes anappropriate amount of light to constantly enter the eye to see thevirtual image through the shading plate, thereby reducing the dilationand contraction of the pupil to relieve the fatigue.

Fourth, the partially transparent shading plate set to provide partialtransmission serves to provide a sufficient front field of view for theexternal sight to alleviate the sense of oppression while the device isin use and to present fields of view and safety appropriate for theoperation, thereby contributing the reduction of the fatigue.

Consequently, the fatigue can be reduced and safety can be ensured bysetting the virtual image forming optical system 3 in front of one ofthe user's eyes and disposing in front of the other eye the partiallytransparent shading plate 4 with a transmittance of less than 1.

FIG. 3 is a model plan describing the position of the partiallytransparent shading plate 4. The virtual image forming optical system 3and the other basic components in this figure are the same as in FIGS. 1and 2. The virtual image forming optical system 3 is located in front ofone of the user's eyes (the left eye 12L in this figure), and the lineof sight glance taken when the user 2 looks in the horizontal directionaligns with an optical path 13 formed by the eye 12L and a virtual image14. The virtual image 14 is seen at a horizontal view of angle ψ. Inthis case, if the other eye 12R sees this virtual image 14 as a realimage, then its horizontal field of view is the area shown by the brokenline. This is also true in the vertical direction, and only the eye 12Lactually sees the virtual image 14. A similar visual operation isprobably performed in the user's brain. Thus, by setting in front of theeye 12R the partially transparent shading plate 4 (or 4') that is atleast larger than the area shown by the broken line, the user 2 can seethe virtual image 14 without overlapping the image 14 and an image ofthe external sight in the corresponding area. The partially transparentshading plate 4 (or 4') can be set in the position of 4 or 4' or anyposition between 4 and 4' as long as its longitudinal position is withinthe longitudinal thickness D of the virtual image forming optical system3 relative to the user's face. Placing the partially transparent shadingplate 4 within the thickness D of the virtual image forming opticalsystem 3 also serves to reduce the size of the device main body.

As described above, the longitudinal position of the partiallytransparent shading plate 4 (or 4') need change its size depending onits longitudinal position. FIG. 4 is a model drawing describing the sizeof the partially transparent shading plate 4. The partially transparentshading plate 4 (or 4') is not necessarily a plane but may be a curvedplate. It is preferable that the shape of a surface 16 projected on anarbitrary surface 15 intersecting the optical axis 13 formed by theuser's eye 12L and the virtual image 14 be approximately similar to thatof a cross section 17 on the interesecting surface 15 of the field ofview for the virtual image formed by the virtual image forming opticalsystem 3 and that the area of the former is equal to or larger than thatof the latter. If this condition is met, a dead angle zone 18 for theeye 12R can be formed around the virtual image 14 by the projectedsurface 16 (that is, the partially transparent shading plate), as shownin FIG. 4. The user 2 can thus view the virtual image 14 withoutoverlapping the image 14 and the external image in the correspondingarea.

As described above, by disposing the partially transparent shading platewith a transmittance of less than 1 in front of the eye that need notsee the virtual image, and setting the size of the shading plate so asto be equal to or larger than that of the field of view for the virtualimage, for optimization, the front and downward fields of view can bemaximized with the visibility of the virtual image maintained, therebyimproving workability and safety.

FIG. 5 shows the results of experiment on the relationship between thesurrounding illuminance and the transmittance of the partiallytransparent shading plate. In this experiment, the surroundingilluminance on the outer surface of the partially transparent shadingplate was varied while the five subjects attempted to subjectivelyoptimize the transmittance of the partially transparent shading plate.The optimized transmittance may serve to balance the above conditions,that is, to prevent a decrease in the contrast of the virtual image, toreduce the dilation and contraction of the pupil, to relieve the senseof oppression while the device is in use, and to provide fields of viewand safety required for the operation. The surrounding illuminanceexpressed on the horizontal axis ranges from the illuminance measuredwhen the lights are put out in an airplane to the illuminance measuredat the window in a room was assumed.

Although a surrounding illuminance of 10001× or higher is expected, thetransmittance of the partially transparent shading plate tends to besaturated at a surrounding illuminance of about 5001×, so thetransmittance of the shading plate is preferably 3% or less regardlessof surrounding illuminance. In addition, if the surrounding illuminanceis 1001× or lower, the transmittance of the partially transparentshading plate should be higher than when the surrounding illuminance ishigher than this value. This is also because doing so enables the aboveconditions to be met.

Methods for controlling the transmittance of the partially transparentshading plate include the use of a partially transparent shading platecomprising a polarizing element or a liquid crystal display element witha polarizing element. In the former case, two polarizing sheets may berotatably placed on each other, and the angle between their transmissionaxes may then be rotationally adjusted to control the transmittance. Thepartially transparent shading plate in this case has a variabletransmittance and is most inexpensive. In the latter case, the partiallytransparent shading plate comprises a liquid crystal display elementconsisting of liquid crystal filled between glass substrates, and, inparticular, a film-type liquid crystal display element consisting ofliquid crystal filled between deformable resins is preferable. In thiscase, the partially transparent shading plate can be formed so as tohave an arbitrary curvature, resulting in the increased degree offreedom in design. In either case, the use of a liquid crystal displayelement enables the construction of a partially transparent shadingplate that is inexpensive, that can be electrically controlled, and thathas a variable transmittance.

FIG. 6 shows the results of experiment on the relationship between thesurrounding brightness (liminance) and the brightness (luminance) of thevirtual image forming optical system. In this experiment, theilluminance around the user was varied, that is, the surroundingbrightness near the user's hands below the device main body was variedwhile the five subjects attempted to subjectively optimize thebrightness of the virtual image forming optical system. The optimizedbrightness may enable the user to see the virtual image most clearlywhen repetitively and alternatively looking at the virtual image andaround the user's hands. The transmittance of the partially transparentshading plate was fixed at 3% according to the results of the experimentin FIG. 5. The surrounding illuminance on the user was set at the samevalue as in the experiment in FIG. 5, and the brightness near the user'shands was measured.

FIG. 6 clearly shows that the surrounding brightness is in proportion tothe brightness of the virtual image forming optical system althoughdifferent subjects revealed somewhat different inclinations and absolutevalues. When the diameters of the subjects' pupils were calculated usingthis brightness data, it was found that they remained almost unchangedeven when the subject was alternatively looking at the virtual image andaround his or her hands. This of course means that the brightness of thevirtual image forming optical system is approximately the same as thebrightness near the subject's hands, and it is expected that the data inFIG. 6 ideally forms a straight line in which Y=X. Of course, when aninput means such as a keyboard which must be viewed by the user duringthe operation is placed near the user's hands during the operation, thebrightness near the user's hands is equal to the brightness on the inputmeans, so the optimum condition in this case is that the brightness ofthe virtual image forming optical system is approximately the same asthe brightness on the input means. This is because the differencebetween the shading of the virtual image forming optical system and theshading near the user's hands or on the input means is minimized whilethe user is repetitively and alternatively looking at the virtual imageand around his or her hands, thereby minimizing the dilation andcontraction of the user's pupil to further minimize the fatigue of themuscles responsible for dilating or contracting the pupil.

Methods for controlling the brightness of the virtual image formingoptical system include the use of a polarizing element, a liquid crystaldisplay element with a polarizing element, or an electrochromic element,and the variation of the brightness of an illumination means in theimage display element. The former two methods involve polarization, andif an image light from the image display element is linearly polarizedto the liquid crystal display element, the enlarging optical means inthe subsequent stage may disturb the polarized light. Thus, this meansis preferably installed between the image display element and theenlarging optical means or between the liquid crystal panel and the backlight. If the polarizing element is used, two polarizing sheets may berotatably placed on each other, and the angle between their transmissionaxes may be rotationally adjusted to control the transmittance, asdescribed in the experiment in FIG. 5. If an image display elementsubject to linear polarization as described above is used, only therotation of a single polarization is required. In any case, this is mostinexpensive method for adjusting brightness. If the liquid crystaldisplay element is used, the degree of freedom in design is improved byusing a liquid crystal display element consisting of liquid crystalfilled between glass substrates, or in particular, a film-type liquidcrystal display element consisting of liquid crystal filled betweendeformable resins, as in the experiment in FIG. 5. An advantage of thismethod is that an electrically controlled brightness adjustmentmechanism can be constructed inexpensively. If the electrochromicelement is used, the installation position is not particularly limited,and a polarizing element is not required as in the former two methods. Abright virtual image forming optical system with a high degree offreedom in design and the highest transmittance can be implemented, anda wide range of the transmittance is available. If the variation of thebrightness of the illumination means in the image display element isused, a control circuit is configured as specifically described in thefollowing embodiment. To achieve the same purpose, however, the voltageof a drive circuit for the illumination means which is part of thecontrol circuit may also be manually controlled.

FIG. 7 shows the virtual image forming optical system and the inputmeans located below. As described above, the virtual image formingoptical system 3 is disposed in front of the user's face so that theoptical axis 13 formed by the user's eye 12 and the virtual image 14approximately aligns with the line of sight taken by the user 2 whenlooking in the horizontal direction. The input means 19 such as akeyboard is located near the user's hands.

This figure shows the ergonomically recommended positional relationshipbetween the user 2 and the input means 19 during a VDT operation. Thatis, the distance from the eye 12 to the tip of the input means 19 isabout 320 mm and the distance from the surface of the input means 19 andthe eye 12 is about 597 mm that is the maximum value for the male. Inthis case, the maximum angle of depression α when the eye 12 sees thetip of the input means 19 can be determined to be about 62°. The user'sfront field of view depends on the virtual image forming optical system3, and the downward field of view is limited by the bottom of thestructure of the virtual image forming optical system 3. In other words,by setting at 62° or less in the vertical direction the angle β betweenthe upper end of the field of view below the structure of the virtualimage forming optical system 3 and the line of sight taken by the user 2when looking in the horizontal direction, the user 2 can view the inputmeans 19 without being disturbed by the structure of the virtual imageforming optical system 3. The above constitution enables the input meanssuch as a keyboard to be placed in an ergonomically optimum position toreduce the fatigue caused by the input operation.

FIG. 8 shows the distance to the virtual image when this image is viewedand the input means when this input means is viewed. As described above,the vertical image forming optical system 3 is disposed in front of theuser's face, and the user 2 sees the virtual image 14 at a distance Afrom the eye 12. The distance A in this case is referred to as a virtualimage perceiving distance. When viewing the input means 19 such as akeyboard located near the user's hands, the user 2 assumes a postureshown in the figure, precisely speaking, with his or her head inclined.A distance B in this case is referred to as a viewing distance.

The user 2 adjusts his or her eye 12 to the virtual image perceivingdistance A when viewing the virtual image 14, while adjusting it to theviewing distance B when viewing the input means 19. Consequently, whenalternatively viewing the virtual image 14 and the input means 19, theuser must adjust his or her eye to the corresponding distance each timethe user changes the target, resulting in the fatigue increasing withincreasing frequency of adjustment. Thus, setting the virtual imageperceiving distance A and the viewing distance B at approximately thesame value substantially eliminates the need of these adjustments,thereby reducing the fatigue caused by the repetition of adjustments.

The virtual image perceiving distance A varies among users due to thedifference among their eyesight and resting positions. Since, however,the allowable range of focusing available to the user is somewhat wide,the virtual image perceiving distance A can be adjusted within thisallowable range. To do this, the relative distance between the imagedisplay element and the enlarging optical means may be varied, and amechanism for moving the image display element and the enlarging opticalmeans in the directions of their respective optical axes may beprovided. In this case, the adjustment can be carried out easily byrepetitively and alternatively viewing the virtual image 14 and theinput means 19 while matching the virtual image perceiving distance Awith the viewing distance B.

FIG. 9 describes the horizontal position in which a virtual image isformed. Table 2 shows the results of experiment that were used todetermine this position.

                  TABLE 2                                                         ______________________________________                                        Subject  Allowable range A  Optimum value                                     ______________________________________                                        1        -1° < A < +5°                                                                      +0.5°                                      2        -1° < A < +4°                                                                      0°                                         3        -1° < A < +4°                                                                      +1°                                        4        -1° < A < +4°                                                                      0°                                         5        -1° < A < +5°                                                                      +1°                                        ______________________________________                                    

Table 2 shows the results of experiment in which five subjects wereprovided with a virtual image forming optical system and asked tosubjectively determine the allowable range of horizontal angles at whichthey can view the virtual image without being subjected to loads as wellas the optimum value within the allowable range. Each angle is formed inthe horizontal direction between a line 23 perpendicular to the user'sface and the optical axis formed by the virtual image and the left eye12L, as shown in FIG. 9. The congestion direction, for example, thedirection of the optical axis 24 in this figure is assumed to bepositive, whereas the opposite direction is assumed to be negative. Theresults in Table 2 can be described in conjunction with FIG. 9. In FIG.9, a single hatching 25 indicates the range of -1° to 5°, whereas adouble hatching 26 denotes the range of 0° to +1°. It can be judged thatthe single hatching area 25 is the allowable range and that the doublehatching area 26 is most preferable.

If the optical axis formed by the user's eye and the virtual image isplaced within these areas, the user 2 can view the virtual image in thedirection in which the image can be seen most clearly with a single eye,without being subjected to loads. The user suffers little fatigue duringnot only short time use but also long time use.

In FIG. 8, the device main body also has on its underside a photosensor20 that acts as a illuminance (brightness) detection means, and theresults of detection by this sensor are fed back to optimize thetransmittance of the partially transparent shading plate and thebrightness of the virtual image forming optical system. As shown in FIG.8 described above, the user 2 has to incline his or her head when movinghis or her line of sight between the virtual image 14 and the inputmeans 19. The detection direction of the photosensor 20 disposed on theunderside of the device main body thus changes between a direction 21and a direction 22 in response to the movement of the device associatedwith the movement of the head. The illuminance from the direction 21(the surrounding illuminance on the outer surface of the partiallytransparent shading plate) detected by the photosensor 20 when the useris viewing the virtual image 14 can be used to control the transmittanceof the shading plate, while the brightness from the direction 22 (thebrightness on the input means 19) detected by the photosensor 20 can beused to control the brightness of the virtual image forming opticalsystem 3. The transmittance and the brightness can thus be automaticallycontrolled on the basis of the relationship described above for FIGS. 5and 6. As a result, both the transmittance of the partially transparentshading plate and the brightness of the virtual image forming opticalsystem can be automatically optimized, so the device main body is alwaysadjusted to its optimal conditions depending on how the user is usingthe device, thereby reducing the user's fatigue.

In the optical arrangement of the virtual image forming optical deviceshown in FIG. 2, the photosensor 20 is most preferably disposed on therear side of the reflection mirror in terms of spatial efficiency anddetection direction. Both of these control means are desirably providedto relieve the fatigue, but the fatigue can be significantly reducedusing only one of the control means.

Next, an example of a control circuit for automatically adjusting thetransmittance of the partially transparent shading plate and thebrightness of the virtual image forming optical system is described withreference to FIGS. 10A, 10B, and 11.

FIGS. 10A and 10B show an example of the use of a liquid crystal displayelement for controlling the transmittance of the partially transparentshading plate; FIG. 10A is a circuit diagram, and FIG. 10B is aflowchart showing a waveform obtained while the liquid crystal displayelement is operating. The photosensor 20 comprises a photodiode 27 and alens 28 that forms input light as an image on the photodiode 27, whichthen outputs a detection signal. This detection signal is amplified byan amplifier 29 and input to a negative terminal of an operationalamplifier 30. A resistor 31 for controlling the voltage is connected toa positive terminal of the operational amplifier 30 to supply a voltagecorresponding to 1001×. The operational amplifier 30 attempts todetermine the amounts of both inputs. If it determines that theilluminance input to the photosensor is larger than the referenceilluminance of 1001×, a switch 38 switches on a signal S1, which isamplified by an amplifier 32 and then input to a liquid crystal displayelement 33. On the contrary, if the operational amplifier 30 determinesthat the illuminance input to the photosensor is smaller than thereference illuminance of 1001×, a switch 39 switches on a signal S2,which is amplified by the amplifier 32 and then input to the liquidcrystal display element 33. If the liquid crystal display element is ina display mode called "Normally Black", and has an amplitude such asshown in FIG. 10B, the transmittance of the partially transparentshading plate decreases when the signal S1 is selected, whereas thetransmittance of the partially transparent shading plate increases whenthe signal S2 is selected, thereby providing desired control. Thetransmittance can be controlled more precisely by increasing the numberof signals.

FIG. 11 is a circuit diagram showing an example of brightness controlprovided by the virtual image forming optical system. A detection signalfrom the photosensor 20 is amplified by an amplifier 34 and then inputto a transistor 35. The voltage of a drive circuit 37 for a fluorescentlight 36 that acts as an illumination means is then controlled accordingto the input voltage. Consequently, the fluorescent light 36 has itsbrightness controlled according to the detection signal from thephotosensor 20, that is, the brightness of the virtual image formingoptical system is controlled.

If the above two controls are used together, changes in the detectiondirection of the photosensor 20 may be confirmed by monitoring for rapidchanges in the detection signal from the photosensor 20, or the movementof the user's head is mechanically detected while the detection signalfrom the photosensor 20 is used to control either the transmittance ofthe partially transparent shading plate or the brightness of the virtualimage forming optical system.

A switching means according to this invention has not been referred toin Embodiment 1, but will be described in detail in Embodiment 2 andsubsequent embodiments described below.

(Embodiment 2)

FIGS. 12 and 13 are model drawings describing a second embodimentaccording to this invention. FIG. 12 is a front view, and FIG. 13 is aside view. Both figures also show the position of an internal opticalsystem. The internal structure of the virtual image forming opticalsystem 3 is the same as in Embodiment 1, so it carries the samereference numerals as in Embodiment 1, and its description is omitted.

The device main body 1 includes the virtual image forming optical system3 located in front of one eye of the user 2. The virtual image formingoptical system 3 extends approximately in the direction of the width ofthe user's eye, and is fictionally fitted via a fixing screw 42 to shaft41 with an approximately cylindrical cross section which engages aholding section 43. The holding section 43 comprises an arm 44, aforehead pad 45, a pad, and a slider 47, as shown in the figure.

The virtual image forming optical system 3 is fictionally fitted via afixing screw 42 to the shaft 41 with an approximately cylindrical crosssection which is fixed to the holding section 43, as described above.When the fixing screw 42 is loosened, the virtual image forming opticalsystem 3 can be then moved on the shaft 41. When the fixing screw 42 istightened again, the virtual image forming optical system 3 isfictionally fitted to the shaft 41, and retained so that it can moveapproximately in the direction of the with of the user's eye along theshaft 41. Thus, the user 2 can easily select the eye 12 to see thevirtual image simply by transversely moving the virtual image formingoptical system 3. Therefore, the head-mounted display device accordingto this embodiment provides high universality and shareability, andenables the user 2 to arbitrarily switch the eye to view the virtualimage between the right and left eyes.

Since the virtual image forming optical system 3 is moved approximatelyin the direction of the width of the user's eye when the eye 12 to viewthe virtual image is switched, the width of the eye can also be adjustedso as to prevent the user from moving his or her eyeballs unnaturally,thereby reducing the fatigue caused by the misalignment of the devicewith the user's eye and simplifying the structure of the associatedadjustment mechanism. Furthermore, since the virtual image formingoptical system 3 is fictionally fitted to the shaft 41 with anapproximately cylindrical cross section, the angle of depression can beadjusted by rotating the virtual image forming optical system 3 aroundthe shaft 41, thereby enabling each user to view optimal images.

The shaft 41 should have a linear portion corresponding to the width ofthe user's eye (max: 72 mm), and the connection between the shaft 41 andthe holding section 43 should have a structure that prevents the shaft41 from being affected by the elastic deformation of the holding section43. The virtual image forming optical system 3 may also be fictionallyfitted to the shaft 41 by using a spring to apply force to the shaft 41.In this case, the fixing screw 42 need not be loosened when the virtualimage forming optical system 3 is moved transversely, resulting insimplified switching operation.

(Embodiment 3)

FIGS. 14 and 15 are model drawings describing a third embodimentaccording to this invention. FIG. 14 is a front view, and FIG. 15 is aside view. Both figures also show the position of an internal opticalsystem. The internal structure of the virtual image forming opticalsystem 3 is the same as in Embodiment 1, so it carries the samereference numerals as in Embodiment 1, and its description is omitted.

The device main body 1 includes the virtual image forming optical system3 located in front of one eye of the user 2. The virtual image formingoptical system 3 is idly retained so as to rotate without affecting thedevice main body 1, and extends in the direction of the width of theuser's eye. The optical system 3 is held on the device main body 1 via ashaft 51 shaped like a screw, and the main body 1 engages the holdingsection 43 via a hinge section 52.

The shaft 51 has a knob 53 at both ends thereof. Rotating the knob 53causes the shaft 51 to rotate without affecting the device main body 1,thereby enabling the virtual image forming optical system 3 spirallyfitted to the shaft 51 to move approximately in the direction the widthof the user's eye. In this case, by providing a guide shaft 54 or aguide plane 54 in the virtual image forming optical system 3 in such away that it sits in parallel with the shaft 51, the virtual imageforming optical system 3 can be moved more stably, and the user 2 cansimply select the eye 12 to view the virtual image. Therefore, thehead-mounted display device according to this invention provides highuniversality and shareability, and enables the user 2 to arbitrarilyswitch the eye to view the virtual image between the right and lefteyes.

Since the virtual image forming optical system 3 is moved approximatelyin the direction of the width of the user's eye when the eye 12 to viewthe virtual image is switched, the width of the eye can also be adjustedso as to prevent the user from moving his or her eyeballs unnaturally,thereby reducing the fatigue caused by the misalignment of the devicewith the user's eye and simplifying the structure of the associatedadjustment mechanism.

In this embodiment, the hinge section 52 engages the device main body 1via a shaft 55 the tip of which is shaped like a screw, and the devicemain body 1 is fixed to the holding section 43 by rotating a control 56located at both ends of the shaft 55 in order to obtain tighteningtorque. Rotating the control 56 to loosen the tightening thus enablesthe angle of depression to be adjusted around the hinge section 52,thereby hindering the user from taking an unnatural line of sight torelieve the fatigue of the eyes. In addition, although the difference inthe user's physique causes the holding section 43 to move upward ordownward or to incline, further triggering similar movement of thedevice main body 1, this movement can be corrected by changing the angleof the device main body 1 around the hinge section 52, thereby avoidingthe misalignment of the virtual image forming optical system 3 with theuser's eye 12 to prevent the fatigue caused by such misalignment.Furthermore, the device main body 1 can be folded toward the holdingsection 43 around the hinge section to save space.

In the embodiment in FIGS. 12 to 15, the holding section 43 comprises anelastic body consisting of a spring steel plate generally made of SUS304 or the like which is covered by a resin. The holding section has anapproximate U-shape, and is supported on the user's forehead by theforehead pad 45 and on the user's head behind the ear by the pad 46. Theforehead pad 45 is mounted so as to cover the forehead before thetemple, and the pad 46 engages the slider 47. Since the almost overallholding section 43 can be uniformly and elastically deformed, it can fitany shape of the head and thus absorb the difference in the user'sphysique, thereby providing high strength, universality, andshareability. In addition, the holding section 43 is supported at threepoints, that is, on the user's forehead and on both sides of the headbehind each ear, so the device can be mounted stably, and eliminates thesense of oppression due to the presence of an empty space above andbehind the user's head. It also prevents the user from feeling tightenedaround the head, and enables the use of a head rest to assume a relaxedposture when sitting in a seat in a travelling body such as an airplane.The user can use this device with spectacles on because the holdingsection 43 is supported on the forehead and on the sides of the headbehind each ear.

As shown in FIGS. 16A and 16B, the slider 47 extends diagonally downwardand has at the tip of its central axis 55 a shaft 56 fitted to a bearingon a slider joint 57. The slider joint 57 has a shaft 59 at its otherend a shaft 59 extending in the direction 58 perpendicular to thecentral axis 55 of the slider 47 and fitted to a bearing on the pad 46.With this configuration, the pad 46 can rotate around the shaft 56 ofthe slider 47 (the direction 60) together with the slider joint 57, andalso rotate in the direction 61 perpendicular to the above directionaround the shaft 59 of the slider joint 57. This enables the pad to fitany shape of the head. Furthermore, if the pad 46 is symmetricalrelative to the shaft 56 of the slider 47, the series of operations canbe performed more smoothly. In addition, the slider 47 comprises aslider A62 and a slider B63 and has a spring and a latch inside, so itcan be allowed to conform to any circumferential length of the head bylongitudinally 64 moving the slider A62 relative to the slider B63.

The device can be mounted further stably by providing an arm 44 with acylindrical cross section in the position corresponding to the top ofthe user's head. The arm 44 has its support point 65 located at the sideend of the slider B63 of the slider 47, comprises an elastic body withan approximate U shape along the top of the user's head, and istelescopic due to its structure similar to the telescopic mechanism ofthe slider 47. The support point 65 of the arm 44 has a structure shownin FIG. 17 to enable the arm 44 to rotate around the X axis (66), the Yaxis (67), and the Z axis (68), relative to the slider 47 to easilyabsorb the effect of the elastic deformation of the holding section 43.The arm 44 can also be folded toward the holding section 43 to savespace. Since the support point 65 of the arm 44 is located at the sideend of the slider B63 of the slider 47, its position relative to the earsubstantially remains unchanged when the slider 47 stretches orcontracts depending on the size of the head, thereby reducing the effectof the difference in the user's physique on safety. In addition, due toits cylindrical cross section, the arm 44 can contact any user's head inan approximately fixed manner and be always mounted stably, wherever onthe top of the head the arm is placed.

(Embodiment 4)

FIGS. 18, 19, and 20 are model drawings showing a fourth invention ofthis invention. FIG. 18 is a front view, FIG. 19 is a side view, andFIG. 20 is an enlarge view of the virtual image forming optical system.

The device main body 1 includes the virtual image forming optical system3 in front of one eye of the user 2. The virtual image forming opticalsystem 3 is retained so as to rotate without affecting the device mainbody 1. The optical system 3 extends approximately in the direction ofthe width of the user's eye, is spirally connected to the shaft 51shaped like a screw and retained on the device main body 1. The opticalsystem 3 also engages the device main body via a guide shaft 70extending in parallel with the shaft 51, and the device main body 1engages a holding section 63 via the hinge section 52. The shaft 51includes the knob 53 at both ends thereof, and rotating the knob 53causes the shaft 51 to rotate without affecting the device main body 1.The virtual image forming optical system 3 spirally connected to theshaft 51 can thus be guided between the shaft 51 and a guide shaft 70 tomove approximately in the direction of the width of the user's eye.

The virtual image forming optical system 3 comprises the image displayelement 9 consisting of the liquid crystal panel 7 and the back light 8for irradiating the liquid crystal panel 7, and the reflection mirror10, and the lens 11 that acts as an enlarging optical means, as in theabove embodiment. An image light formed and output by the image displayelement 9 has its optical path changed by the reflection mirror 10, andis then formed by the lens 11 as an image in the user's eye 12 to viewthe virtual image. If the image formation surface of the image displayelement 9 is disposed between the object side focus of the lens 11 andthe lens 11 and the eye 12 to view the virtual image is located near theimage side focus of the lens 11, the image forming effect of the lens 11allows the enlarged virtual image 14 of screen information to be seen onthe extension of the optical axis 13 of the virtual image formingoptical system 3. The partially transparent shading plate 4 isresponsible for shading the eye that need not view the virtual image,for example, the right eye 12R, and setting the transmittance of thepartially transparent shading plate at 1 or less causes the contrast toappear to the user to have increased, resulting in good visibility.

As shown in FIG. 18, since the partially transparent shading plate 4 isdisposed in front of the user's eyes, in a space opposite to the user 2relative to virtual image forming optical system 3, and at least allover the virtual image formation area within the movement area of thevirtual image forming optical system 3, the removal and mounting of thepartially transparent shading plate 4 are not required when the knobs 53are rotated to move the virtual image forming optical system 3. Thus,the user 2 can simply change the eye to view the virtual image. In thiscase, the reflection mirror 10 is disposed at an angle of approximately45° from the vertical direction, so the lower end of the partiallytransparent shading plate 4 is prevented from jumping forward by placingthe shading plate 4 at an angle of approximately 45° from the verticaldirection as shown in FIG. 21. This contributes to the reduction of thesize of the device main body 1. In this case, applying antireflectionprocessing to the user 2 side surface A72 of the partially transparentshading plate 4 can prevent reflection from the surface B74 of apartition 73 that opposes to the surface A72 and the surrounding lightfrom affecting the surface A72, leading to further improved visibility.The partition 73 is provided to protect a drive circuit 75 disposedthereover.

In FIGS. 18 to 21, the image display element 9 is fixed inside a frame76 including a rack section, a gear 77 that engages the rack section isdisposed in front of the frame 76. A diopter adjustment control 78 isfixed to each side of the gear 77 via a screw 79. To adjust diopter, thediopter adjustment control 78 is rotated around a portion fixed by thescrew 79 so as to draw an arc. This operation causes the gear 77 torotate to move the image display element 9 upward or downward in orderto vary the relative distance between the image display element 9 andthe lens 11. According to this embodiment, the diopter adjustmentcontrol 78 is installed on both sides of the virtual image formingoptical system 3, and each diopter adjustment control 78 moves togetherwith the other. The user 2 has only to operate one of the diopteradjustment controls 78 of the virtual image forming optical system 3 toadjust diopter. Thus, whether the virtual image forming optical system 3has been switched to the right or left, the user 2 can operate thecorresponding diopter adjustment control from the corresponding sideusing the corresponding hand, resulting in improved operability ofdiopter adjustment. The operability can further be improved by employinga support structure with which the partially transparent shading plate 4can be opened and closed in front of the user 2 in order to enable theuser 2 to operate the diopter adjustment control 78 with the partiallytransparent shading plate 4 opened frontward, as shown in FIGS. 22 and23.

As shown in FIG. 20, the image display element 9 and the drive circuit75 for the image display element 9 which is fixed and disposed outsidethe movement space for the transverse movement of the virtual imageforming optical system 3 are connected together via a flexible printedcircuit (FPC) 82. The FPC 82 can improve the flexibility of the cablebetween the virtual image forming optical system 3 and the drive circuit75 for the image display element 9 when the knobs 53 are rotated to movethe optical system 3. As a result, the virtual image forming opticalsystem 3 can be moved reliably and smoothly. The virtual image formingoptical system 3 can also be moved within a cable housing space with asmall height, thereby contributing to the reduction of the size of thedevice main body 1.

In FIG. 21, the substrate of the drive circuit 75 for the image displayelement 9 has circuit elements on its top side and an FPC connector 83on its bottom side, and the drive circuit 75 and the virtual imageforming optical system 3 are connected together through a guide hole 84in the partition 73 via the FPC 82.

As shown in FIGS. 20 and 21, the drive circuit 75 should be flatlyplaced outside the movement space for the transverse movement of thevirtual image forming optical system 3 in approximately parallel withthe direction of the width of the user's eye. This improves the heatrelease effect of the drive circuit 75 to improve the reliability of thecircuit. In addition, the flat placement of the drive circuit 75 servesto increase the packaging area for circuit parts to reduce the circuitspace in the height direction. Furthermore, the FPC 82 is attached to orremoved from the drive circuit 75 in the direction of the transversemovement of the virtual image forming optical system 3, and the guidehole 84 for guiding the FPC 82 approximately perpendicularly to thelateral movement of the virtual image forming optical system 3 isprovided in the partition 73 disposed between the FPC connector 83 andthe image display element 9. This constitution hinders stress from beingapplied to the FPC connector 83 and FPC 82 to prevent the FPC 82 frombeing accidentally removed, thereby enabling the virtual image formingoptical system 3 to move transversely smoothly and reducing the size ofthe device. In addition, the guide hole 84 is provided in the partition73, and has only to be located in a position in which the FPC 82 can beguided approximately perpendicularly to the direction of the lateralmovement of the virtual image forming optical system 3. If, however, itis provided in that position of the drive circuit 75 which correspondsto the center line 85 of the user 2, the length of the FPC 82 can beminimized to reduce unwanted slack, thereby enabling the virtual imageoptical system 3 to move laterally smoothly.

(Embodiment 5)

FIGS. 24 and 25 are model drawings showing a fifth embodiment of thisinvention. FIG. 24 is a front view, and FIG. 25 is a side view. FIG. 24is partially shown in cross section for explanation.

The basic configuration of this embodiment is similar to that of theabove embodiment, and is characterized by the provision of anantidominant eye determination support means 93. As mentioned inEmbodiment 1, the eye to view the virtual image desirably has a poorereyesight to reducing the fatigue of the eyes.

In this embodiment, to determine the antidominant eye that should beallowed to view the virtual image, the antidominant eye determinationsupport means 93 is provided in the approximate center 85 of the widthof the user' eye. The antidominant eye determination support means 93comprises a band-like material as shown in FIG. 24, and is positionedbetween the near point of the user's eyes and the user. This means isthus defocusing for the user' eyes, but its position and shape can beidentified as long as it has an appropriate size. The antidominant eyedetermination support means 93 can be seen by both eyes by placing it inthe approximate center of the width of the user's eye and outside thevirtual image forming optical system 3 in front of the eye 12 to viewthe virtual image.

It is assumed that the user's right eye has a better eyesight. The user2 mounts the device main body 1 on his or her head, and position thevirtual image forming optical system 3 in front of his or her left eye.FIG. 26A shows the relative positions of a virtual image 94 formed bythe virtual image forming optical system 3 and an image of theantidominant eye determination support means 93 as seen by both eyes,and FIG. 26B shows the misalignment of the relative positions observedwhen the right eye 12R that need not view the virtual image is closed.FIG. 26C shows the relative positions determined when the images areviewed by both eyes with the virtual image forming optical system 3located in front of the right eye 12R with a better eyesight, and FIG.26C shows the relative positions determined when the left eye 12L thatneed not view the virtual image is closed. These misalignments arecompared, and the left eye, which was being tested when a largermisalignment occurred, is determined to be the antidominant eye, and thevirtual image forming optical system 3 is moved to the antidominant eyeto allow it to view the virtual image. There is no restriction on whicheye should be tested first. If the antidominant eye determinationsupport means 93 can be housed in the device main body after theantidominant eye determination, it will not obstruct the user duringoperations.

(Embodiment 6)

FIGS. 27, 28, and 29 are model drawings showing a sixth embodiment ofthis invention. FIG. 27 is a front view, and FIG. 28 and 29 are sideviews.

In this embodiment, the device main body 1 has a partially transparentshading plate 92 sized to partially cover the fields of view of botheyes of the user 2, outside the virtual image forming optical system 3relative to the user 2. In a monocular type head-mounted display device,the partially transparent shading plate 92 prevents decreases in thecontrast of virtual image information caused by optical informationincident on the eye that need not view the virtual image (the right eye12R in this figure). The partially transparent shading plate 92 ispositioned outside the movement space of the virtual image formingoptical system 3, and can partially remove information supplied to theeye 12R that need not view the virtual image, regardless of the movementof the optical system 3 to the user's right or left eye, as describedabove.

In this embodiment, the partially transparent shading plate 92 has anantidominant eye determination support means 95 in the approximatecenter 85 of the width of the user's eye. The antidominant eyedetermination support means 95 is a slit provided in the partiallytransparent shading plate 92 as shown in FIG. 27, and has an appropriatesize to be identified by the user 2 despite defocusing, as in the aboveembodiment.

The antidominant eye determination support means 95 provided in thepartially transparent shading plate 92 is located in dead space andobstructed by the virtual image forming optical system 3 when the devicemain body is mounted on the user's head. The device main body 1 is thusconnected to the holding section 43 via the hinge section 70 so that theantidominant eye determination support means 95 can be identified byboth eyes by moving the virtual image forming optical system 3 via thehinge section 70 in the direction shown by arrow B. The relativepositions of external sight information 96 and an image of theantidominant eye determination support means 95 as seen by both eyes, orthe right or left eye are described with reference to FIGS. 29A and 29B.These figures show an example in which the user's dominant eye is theright eye. FIG. 29A shows the relative positions determined when theimages are viewed first with both eyes and subsequently with only theright eye. FIG. 29B shows the relative positions determined when theimages are viewed first with both eyes and subsequently with only theleft eye. These relative positions are compared, and the eye beingtested when a larger misalignment occurred, that is, the left eye in theexample in FIGS. 29A and 29B is determined to be an antidominant eye.

The antidominant eye determination support means 95 is located fartherfrom the user 2 than the antidominant eye determination support means 93in the above embodiment, and closer to the near point of the user'seyes, so this means can be seen more easily to enable the aboveantidominant eye determination to be conducted more easily. Theantidominant eye determination support means 95 is not limited to a slitas long as it has a sufficient size and color to be identified by theuser 2. It may be, for example, a round hole, an LED, a printedmaterial, or paint.

Furthermore, moving the virtual image forming optical system 3 to abovethe user's head enables the antidominant eye determination means 93 inthe above embodiment to be used as shown in FIG. 30 to enable theantidominant eye determination to be conducted similarly.

(Embodiment 7)

FIGS. 31A and 31B are enlarged views of a head-mounted display deviceaccording to a seventh embodiment of this invention, and show the partdesignated by reference numeral 96 in FIG. 29.

In the above embodiment, when the slit that is the antidominant eyedetermination support means 95 is moved to above the user's head toprevent the antidominant eye determination support means 95 from beingobstructed by the virtual image forming optical system 3. Thisembodiment employs a different means to enable the antidominant eyedetermination support means 95 to be seen by both eyes.

As in the above embodiment, the virtual image forming optical system 3is retained on the device main body 1 via the shaft 51 shaped like ascrew extending in the direction of the width of the user's eye, theshaft 51 including the knob 53 at both ends thereof. The optical system3 is also retained so as to be moved in the direction of the width ofthe user's eye when the knob 53 is rotated as shown in FIG. 31A. In thiscase, the shaft 53 has a length at which the virtual image formingoptical system 3 can move over the width of the user's eyes or longer.The maximum width of human eyes is generally 72 mm, so the virtual imageforming optical system 3 must be able to move laterally over this lengthor longer. That is, any user can see the antidominant eye determinationsupport means 95 with both eyes as long as the shaft 53 has a length atwhich the eye to view the virtual image can see the antidominant eyedetermination support means 95 from the inner surface of the virtualimage forming optical system 3.

As a result, the virtual image forming optical system 3 can be simplymoved outside the right or left line of sight to a position in which theantidominant eye determination support means 95 can be identified withboth eyes, as shown in FIG. 31B, and the relative positions determinedwhen the images are viewed by both eyes, the right or left eye can becompared to determine the antidominant eye eyesight, as in the aboveembodiment. The comparison of the relative positions of the virtualimage and the antidominant eye determination support means 95 is thesame as in FIGS. 29A and 29B.

(Embodiment 8)

FIGS. 32 and 33 are model drawings showing an eighth embodiment of thisinvention. FIG. 32 is a front view, and FIG. 33 is a side view. As inthe above embodiments, like components carry like reference numerals,and their explanation is thus omitted.

In the above antidominant eye determination, one of the user's eyes mustbe closed. The muscle around the open eye may thus somewhat contract andaffect the antidominant eye determination. Thus, in this embodiment, ashading means 97 for allowing the eye to view the virtual image to bearbitrarily selected among both eyes, one of the eyes, or the other eyeis provided between the device main body 1 and the user 2 to enable theuser to determine the antidominant eye without closing his or her eye.The shading means 97 is shaped like spectacles, and its shading sectioncomprises a liquid crystal display element and a polarizing element. Thetransmittance of the shading section is controlled by using a shadingselection switch 97a provided on both sides of the shading means 97;each time the switch is pressed, shading and transmission arealternatively provided. The shading selection switches 97a areindependent of each other, and shading and transmission arealternatively provided for the eye corresponding to the pressed switch.In FIG. 34, light is shaded on the right eye side while it istransmitted on the left eye side. By repeating this operation, both eyesor a single eye can be allowed to view the images. If the shading means97 comprises a polarizing element, the fields of view in front of eacheye can be mechanically and arbitrarily blocked by providing a slidingswitch on the underside of the shading means 97. The shading means 97may be integrated with the device main body 1.

(Embodiment 9)

FIGS. 35 to 38 are flowcharts describing a method for mounting thehead-mounted display device on the user's head according to theembodiments of this invention. FIG. 35 explains the mounting of theoverall device before the start of operation. FIG. 36 describes theantidominant eye determination method in the embodiment in FIGS. 24 and25. FIG. 37 explains the antidominant eye determination method in FIGS.27, 28, 30, 31A, and 31B. FIG. 38 describes the antidominant eyedetermination method in the embodiment in FIGS. 32 and 33.

As described above, since it has been found that allowing theantidominant eye to view the virtual image serves to reduce the fatigue,the device main body in this invention has a structure for determiningthe antidominant eye. To prevent the fatigue caused by mistakes in theselection of the eye to see the virtual image or the mounting of thedevice, the procedure for mounting the device main body on the user'shead before initiating an operation is explained below.

As shown in FIG. 35, device main body 1 is held on the user's head sothat the antidominant eye determination support means 93 or 95 islocated in the approximate center of the width of the user's eye. Theantidominant eye determination method of the corresponding embodiment isthen used to conduct the above test (S1) to determine the user'santidominant eye (S2). The knob 53 is subsequently rotated to shift thevirtual image forming optical system 3 to the antidominant eye (S3),while simultaneously the width of the eye is adjusted. The diopteradjustment control 78 is used to control diopter while viewing thevirtual image 14 (94, 96) (S4). The mounting of the device is finishedwhen the brightness of the back light has been adjusted to an optimumvalue.

FIG. 36 shows the procedure for the antidominant eye determinationmethod according to Embodiment 5. The antidominant eye determinationmeans 93 is placed in the approximate center of the fields of view ofthe user's eyes (S10), and the virtual image forming optical means 3 ispositioned in front of one of the eyes (S11). Both eyes are allowed toview an image of the antidominant eye determination support means 93 andan image formed by the virtual image forming optical system 3 todetermine their relative positions (A) (S12). The relative positions (B)are again determined with the eye that need not view the virtual image12b closed (S13). (A) and (B) are compared to memorize the amount ofmisalignment (C) (S14). The virtual image forming optical means 3 isthen moved to the opposite eye and a similar procedure is used todetermine the amount of misalignment (F) (S15, S16, S17). (C) and (F)are compared (S18), and the eye being tested when a larger misalignmentoccurred is determined to be the antidominant eye (S19, S20, S21).

The procedure for Embodiments 6 and 7 is shown in FIG. 37. Since theantidominant eye determination means 93 is located in dead space withrespect to the eye to view the virtual image, the virtual image formingoptical means 3 is moved via the hinge section 52 to above the user'shead to a position in which the antidominant eye determination means 93can be seen by both eyes, or the knob 53 is rotated to move it in thedirection of the width of the user's eye (S31). The same method asdescribed above is used to determine the antidominant eye (S32 to S40).

FIG. 38 shows the procedure for Embodiment 8. As in FIG. 37, the virtualimage forming optical means 3 is moved, the shading means 97 isinstalled between the device main body 1 and the user 2, and one of theshading selection switches located adjacent to the respective eyes isarbitrarily selected to allow one of the eyes to view the images. Theshading means 97 is subsequently housed, and the virtual image formingoptical means 3 is set in front of the antidominant eye determined.

These procedures enable the smooth and easy determination of theantidominant eye that is allowed to view the virtual image in order toprevent the wrong selection of the eye to view the virtual image and theresulting fatigue, whichever of Embodiments 5 to 8 may be used. They canalso prevent the fatigue caused by mistakes in the mounting of thedevice.

(Embodiment 10)

FIGS. 39 and 40 are model drawings showing a tenth embodiment of thisinvention. FIG. 39 is a front view, and FIG. 40 is a side view. Thevirtual image forming optical system 3 is the same as in, for example,the embodiment in FIG. 20, and its description is thus omitted.

The structure in FIGS. 39 and 40 has the same basic constitution as thestructure according to the embodiment in FIGS. 27 and 28.

In this embodiment, the device main body 1 is disposed opposite to theuser 2 relative to the virtual image forming optical system 3 andoutside the movement space of the optical system 3, and includes thepartially transparent shading plate 92 that partially covers the fieldsof view of both eyes of the user 2. The partially transparent shadingplate 92 is generally used in monocular type head-mounted displaydevices to prevent decreases in the contrast of virtual imageinformation caused by optical information incident on the eye that neednot view the virtual image (the right eye 12R in the example shown inthe figure). In this embodiment, since the partially transparent shadingplate 92 is positioned outside the movement area of the virtual imageforming optical system 3, it can partially remove information suppliedto the eye that need not view the virtual image, regardless of themovement of the optical system 3 to the user's right or left eye.

While the device main body 1 is in operation, the optical axis 13 of thevirtual image forming optical system 3 (see FIG. 20) must align with theuser's line of sight. Since, however, the head-mounted display device ismounted on the user's head, the distance between the lens 11 and the eyeto view the virtual image varies depending on the shape of the user'shead. The lens 11 is usually set so as to have a relatively wideeffective area to compensate for the variation. Thus, if the opticalaxis 13 of the virtual image forming optical system 3 somewhat deviatesfrom the user's line of sight within the effective area, the user 2sometimes fails to notice this misalignment and suffers fatigue.

In this embodiment, to prevent such misalignment, a slit 100 that actsas a location mark is provided on the partially transparent shadingplate 92 in the intermediate position between the virtual image formingoptical system 3 as placed in front of the user's right eye and the sameoptical system 3 as placed in front of the user's left eye. Thepartially transparent shading plate 92 is disposed between the nearpoint of the user's eye and the user 2, so the slit 100 on the shadingplate 92 is of course defocusing with respect to the user's eye. Theposition of the slit 100, however, can be identified as long as it hasan appropriate size. Thus, after mounting the device main body 1 on hisor her head, the user 2 can generally align the slit 100 with the user'scenter line 85 by rotating the device main body 1 around his or her headso that the slit 100 aligns with the center of his or her face. Thisreduces the occurrence of the fatigue caused by misuse includingmisalignment. The location mark that acts as a center determinationsupport means is not limited to the slit 100 as long as it has asufficient size and color to be identified by the user 2. It may be, forexample, printing or paint on the partially transparent shading plate92.

(Embodiment 11)

FIG. 41 is a side view of a head-mounted display device representing aneleventh embodiment of this invention.

In this embodiment, the device main body 1 has a nose support means 101that acts as a center determination support means, in the intermediateposition between the virtual image forming optical system 3 as placed infront of the user's right eye and the same optical system 3 as placed infront of the user's left eye. The nose support means 101 is installed onthe device main body 1 and has a rotational support point 102 outsidethe movement space of the virtual image forming optical system 3. Theoverall nose support means 101 is movably supported outside the movementspace of the virtual image forming optical system 3, as shown by thebroken line in the figure. The nose support means 101 includes a nosesupport section 103 that sits astride the user's nose and an adjustmentsection 104 for adjusting the length of the nose support means 101, andthe nose support section 103 can be moved in the axial direction of thenose support means 101 by rotating the adjustment means 104.

In this configuration, the user 2 can align his or her center line 85with the intermediate position between the virtual image forming opticalsystem 3 as placed in front of the user's right eye and the same opticalsystem 3 as placed in front of the user's left eye by mounting thedevice main body 1 on his or her head and adjusting the length of thenose support means 101 so that it sits astride the user's nose. Bysubsequently moving the nose support means 101 to outside the movementspace of the virtual image forming optical system, the virtual imageforming optical system 3 can be switched to the right or left withouthinderance. The nose support means 101 may be moved to the outside themovement space of the virtual image forming optical system 3 only whenthe optical system is to be moved, or may be allowed to contact theuser's nose only when the center is to be determined and otherwisehoused in the device main body 1. The latter method is effective if theuse of this means with spectacles is cumbersome or the user feels sickof constant contact with this means.

As described above, this embodiment also reduces the occurrence of thefatigue caused by the misuse of the device including misalignment.

(Embodiment 12)

FIG. 42 is a front view of a head-mounted display device representing atwelfth embodiment of this invention.

The center determination support means in FIG. 42 is the slit 100described in Embodiment 10 above, and the user 2 determines the centerof the device main body 1 as described above. Before viewing the virtualimage, the user 2 also rotates the knob 53 to select the view to see thevirtual image and to adjust the width of the user's eye. An indication104 shown in FIG. 42 is provided on the partially transparent shadingplate 92 and a wall above the shading plate. Since the partiallytransparent shading plate 92 partially transmits light, viewing thedevice main body 1 frontways enables the movement of the virtual imageforming optical system 3 to be read from the graduation behind which thereference surface (for example, the user's nose side of the opticalsystem 3) of the optical system 3 is situated.

Thus, if the user 2 must repetitively use the device, misalignment canbe further hindered by reading the movement of the virtual image formingoptical system 3 to move it to the determined position before mountingthe device main body 1, in combination with the subsequent centerdetermination.

The indication 104 is not limited to the one shown in FIG. 42, but maybe numbers directly corresponding to the width of the user's eye or amarker movably and fixably provided for indicating the movement of thevirtual image forming optical system 3. Of course, instead of the slit100, the above nose support means 101 may be used for the centerdetermination support means.

(Embodiment 13)

FIG. 43 is a partially enlarged view showing peripheral mechanisms forthe knob 53 in the above embodiment, and shows the part (a) in FIG. 39.

In this figure, the virtual image forming optical system 3 extendsapproximately in the direction of the width of the user's eye, and isretained via a screw-like shaft 105 so as to move approximately in thedirection of the width of the user's eye. Due to its non-screw section106 fitted in the device main body 1, the shaft 105 is retained so as torotate without affecting the device main body 1. The shaft 105 hasbeyond the non-screw section another screw section 107 that connects tothe knob 53. A fixture 108 is spirally connected to the screw section107. For simplification, only one end of the shaft 105 is shown, but theother end has a similar configuration.

A switching means including a fixing mechanism of the above constitutioncarries out switching as follows. When the knob 53 is rotated, the shaft105 moves, according to the rotation, to rotate without affecting thedevice main body 1. The virtual image forming optical system 3 spirallyconnected and fitted to the shaft 105 thus moves approximately in thedirection of the width of the user's eye. After the virtual imageforming optical system 3 has moved to a desired position, the fixture108 is rotated so as to contact the side wall of the device main body 1.Then, the knob 53 can no longer be rotated. Conversely, if under theseconditions, the virtual image forming optical system 3 is to be movedagain, the fixture 108 is rotated reversely so as to leave the side wallof the device main body 1.

Consequently, if the same user must repetitively view images,misalignment can further be hindered due to the pre-fixture of thevirtual image forming optical system 3 to the user's optimum position,in combination with the subsequent center determination.

(Embodiment 14)

FIG. 44 is a model drawing showing a fourteenth embodiment of thisinvention, and shows an enlarged view of an internal optical system.

In the virtual image forming optical system 3, an image light formed andoutput by the image display element 9 has its optical path changed by apartially transparent mirror 110, and is then formed by the lens 11 asan image in the user's eye 12. If the image formation surface of theimage display element 9 is disposed between the object side focus of thelens 11 and the lens 11 and the eye 12 to view the virtual image islocated near the image side focus of the lens 11, the image formingeffect of the lens 11 allows the enlarged virtual image 14 of screeninformation to be seen on the extension of the optical axis 13 of thevirtual image forming optical system 3. This embodiment also has a pupildetection means comprising a pupil detection sensor 111 and an infraredLED 112, on the transmission axis of the partially transparent mirror110 and in a position corresponding to the optical axis 13 of thevirtual image forming optical system 3.

An infrared light output from the infrared LED 112 penetrates thepartially transparent mirror 110, is then reflected by the user's pupil,and again penetrates the partially transparent mirror 110. The light isthen received by the pupil detection sensor 111 to detect its intensityin order to detect the position of the pupil. By rotating the control 53(see FIG. 45,etc.) protruding sideward, the shaft 51 is rotated withoutaffecting the device main body 1. The virtual image forming opticalsystem 3 spirally connected to the shaft 51 can thus be movedapproximately in the direction of the width of the user's eye. In thiscase, the virtual image forming optical system 3 can be moved morestably by providing the optical system 3 with a guide shaft 113 or aguide plane in parallel with a shaft A4.

To move and position the virtual image forming optical system 3 in frontof the right or left eye, the user 2 rotates the control 53 of the shaft51 to put out the back light 8. After moving the virtual image formingoptical system 3 approximately to a position in which the overallvirtual image 14 can be seen, the user lights the infrared LED 112located behind the partially transparent mirror 110, uses the pupildetection sensor 111 to measure the intensity of infrared lightreflected from the pupil, and feeds the result back to the drive circuit75. The drive circuit 75 compares data on the quantity of reflectedlight transmitted from the pupil detection sensor 111, to the presetquantity of reflected light. If the quantity in the data is not equal tothe set value, a means for informing the user of misalignment is used toalarm the user 2. To do this, for example, a buzzer 115 (see FIG. 45)may be activated, the image from the image display element may beallowed to disappear with the back light 8 prevented from turning on, oran image such as an alarm indication may be allowed to overlap thevirtual image 14.

A simple alarm such as a buzzer sound serves to simplify theconstitution of the device, and the user can notice it easily. If theimage from the image display element 9 is allowed to disappear, the usercannot see the image unless he or she corrects the misalignment. Thismethod can thus prevent the misuse of the device due to the misalignmentof the user's pupil 114 with the virtual image forming optical system 3,and the user can notice the misuse without affecting surrounding people.If a specific image is allowed to overlap the virtual image, the usercan notice the misuse without affecting surrounding people, even undernoisy conditions, or even if he or she is hard of hearing.

As described above, according to this embodiment, the virtual imageforming optical system 3 can be moved approximately in the direction ofthe width of the user's eye, and the pupil detection means can be usedto accurately and easily adjust the position of the optical system 3 tothe position of the pupil. As a result, the user 2 is prevented frommoving his or her eyeballs unnaturally, so the fatigue of the eyescaused by the misalignment of the user's pupil with the device isavoided, and the structure of the associated adjustment mechanisms issimplified.

In addition, since the pupil detection means is provided on thetransmission axis of the partially transparent mirror 110 and in aposition corresponding to the optical axis 13 of the virtual imageforming optical system 3, the constitution of this means can besimplified, and the position of the user's pupil can be detected withoutincreasing the size of the device main body.

(Embodiment 15)

FIG. 45 is a model drawing showing a fifteenth embodiment of thisinvention, and shows an enlarged view of an internal optical system.

In the virtual image forming optical system 3, an image light formed andoutput by the image display element 9 penetrates the partiallytransparent mirror 110, and is formed by the lens 11 as an image in theuser's eye 12. If the image formation surface of the image displayelement 9 is disposed between the object side focus of the lens 11 andthe lens 11 and the eye 12 to view the virtual image is located near theimage side focus of the lens 11, the image forming effect of the lens 11allows the enlarged virtual image 14 of screen information to be seen onthe extension of the optical axis 13 of the virtual image formingoptical system 3. The partially transparent mirror 110 is disposed onthe optical path between the image display element 9 and the eye 12, andthe pupil detection means comprising the pupil detection sensor 111 andinfrared LED 112 is located on the reflected light path of the partiallytransparent mirror 110 and in a position corresponding to the opticalaxis 13 of the virtual image forming optical system 3.

An infrared light output from the infrared LED 112 is reflected by thepartially transparent mirror 110, then by the user's pupil, and thenagain by the partially transparent mirror 110. The light is thenreceived by the pupil detection sensor 111 to detect its intensity inorder to detect the position of the pupil.

To move and position the virtual image forming optical system 3 in frontof the right or left eye, the user 2 rotates the control 53 (see FIG.45, etc.) of the shaft 51 to put out the back light 8. After moving thevirtual image forming optical system approximately to a position inwhich the overall virtual image 14 can be seen, the user lights theinfrared LED 112 located on the reflection axis of the partiallytransparent mirror 110, uses the pupil detection sensor 111 to measurethe intensity of infrared light reflected from the pupil, and feeds itsresult back to the drive circuit 75. The drive circuit 75 compares dataon the quantity of reflected light transmitted from the pupil detectionsensor 111, to the preset quantity of reflected light. If the quantityin the data is not equal to the set value, a means for informing theuser of misalignment, for example, the buzzer 115 is used to inform theuser 2 of the misalignment.

As described above, the virtual image forming optical system 3 can bemoved approximately in the direction of the width of the user's eye, andthe pupil detection sensor 111 can be used to accurately and easilyadjust the position of the optical system 3 to the position of thepupil. As a result, the user 2 is prevented from moving his or hereyeballs unnaturally, so the fatigue of the eyes caused by themisalignment of the user's pupil with the device is avoided, and thestructure of the associated adjustment mechanisms is simplified.

In addition, since the partially transparent mirror 110 is disposed onthe optical path between the image display element 9 and the user'spupil, this device can be applied to the virtual image forming opticalsystem 3 of a linear arrangement such as shown in FIG. 45, therebyenabling the user's pupil to be detected without increasing the size ofthe device main body.

(Embodiment 16)

FIG. 46 is a model drawing showing a sixteenth embodiment of thisinvention, and shows an enlarged view of an internal optical system.

After penetrating a partially transparent mirror 116, an image lightformed and output by the image display element 9 has its optical pathchanged by the partially transparent mirror 110, and is then formed bythe lens 11 as an image in the user's eye. If the image formationsurface of the image display element 9 is disposed between the objectside focus of the lens 11 and the lens 11 and the eye 12 to view thevirtual image is located near the image side focus of the lens 11, theimage forming effect of the lens 11 allows the enlarged virtual image 14of screen information to be seen on the extension of the optical axis 13of the virtual image forming optical system 3. The pupil detection meanscomprising the pupil detection sensor 111 and infrared LED 112 islocated on the reflected light path of the partially transparent mirror116 and in a position corresponding to the optical axis 13 of thevirtual image forming optical system 3.

An infrared light output from the infrared LED 112 is reflected by thepartially transparent mirror 116, then by the partially transparentmirror 110, then by the user's pupil, and then again by the partiallytransparent mirror 110. The light is then reflected by partiallytransparent mirror 116, and received by the pupil detection sensor 111to detect its intensity in order to detect the position of the pupil.

To move and position the virtual image forming optical system 3 in frontof the right or left eye, the user 2 rotates the control 53 (see FIG.45) of the shaft 51 to put out the back light 8. After moving thevirtual image forming optical system approximately to a position inwhich the overall virtual image 14 can be seen, the user lights theinfrared LED 112 located on the reflection axes of the partiallytransparent mirrors 110 and 116, uses the pupil detection sensor 111 tomeasure the intensity of infrared light reflected from the pupil, andfeeds the result back to the drive circuit 75. The drive circuit 75compares data on the quantity of reflected light transmitted from thepupil detection sensor 111, to the preset quantity of reflected light.If the quantity in the data is not equal to the set value, for example,the buzzer 115 is used to inform the user 2 of the misalignment, as inthe above embodiments (14 and 15).

As described above, according to this embodiment, the virtual imageforming optical system 3 can be moved approximately in the direction ofthe width of the user's eye, and the pupil detection means can be usedto accurately and easily adjust the position of the optical system 3 tothe position of the pupil. As a result, the user 2 is prevented frommoving his or her eyeballs unnaturally, so the fatigue of the eyescaused by the misalignment of the user's pupil with the device isavoided, and the structure of the associated adjustment mechanisms issimplified.

In addition, since the partially transparent mirror 116 is disposed onthe reflection axis of the partially transparent mirror 110, the pupildetection means does not obstruct the field of view, and the applicationof this device to the see-through-type virtual image forming opticalsystem 3 such as shown in FIG. 46 becomes possible. In addition, theangle of incidence of light on the partially transparent mirror 116 isset at a small value, so the user's pupil can be detected withoutincreasing the size of the device main body 1.

If the power of the lens 11 must be canceled to view the external sight,a lens that functions to cancel the power of the lens 11 may be disposedon the transmission axis of the partially transparent mirror 110.

(Embodiment 17)

FIGS. 47 and 48 are model drawings showing a fourteenth embodiment ofthis invention. FIG. 47 is a top view, and FIG. 48 is a side view. Theinternal structure of the virtual image forming optical system 3 is thesame as in the embodiment in FIG. 44, and its description is thusomitted.

The device main body 1 includes the virtual image forming optical system3 located in front of one eye of the user 2. The virtual image formingoptical system 3 is spirally connected to the shaft 51 retained so as torotate without affecting the device main body 1, extending approximatelyin the direction of the width of the user's eye, and shaped like ascrew, and engages the holding section 43. The shaft 51 has on its sidea motor 116 that acts as a drive means, and driving the motor 116 causesthe shaft 51 to rotate without affecting the device main body 1. Thevirtual image forming optical system 3 spirally connected to the shaft51 can thus be moved approximately in the direction of the width of theuser's eye. The virtual image forming optical system 3 can be moved morestably by providing the optical system 3 with the guide shaft 113 or theguide plane in parallel with the shaft 51.

To move and position the virtual image forming optical system 3 in frontof the right or left eye, the user 2 puts out the back light 8, uses thepupil detection sensor 111 to detect the position of his or her pupil,and feeds the result back to the drive circuit 75. The drive circuit 75compares data on the quantity of reflected light transmitted from thepupil detection sensor 111, to the preset quantity of reflected light.Based on the results of the comparison, the drive circuit 75 controlsits own driving power for moving the virtual image forming opticalsystem 3.

As described above, the virtual image forming optical system 3 can bemoved approximately in the direction of the width of the user's eye, andthe pupil detection sensor 111 can be used to accurately and easilyadjust the position of the optical system 3 to the position of thepupil. As a result, the user 2 is prevented from moving his or hereyeballs unnaturally, so the fatigue of the eyes caused by themisalignment of the user's pupil with the device is avoided, and thestructure of the associated adjustment mechanisms is simplified.

Furthermore, positions can be automatically adjusted, so the device canbe mounted easily, and the mounting and removal of the device can berepetitively carried out in the same manner.

The position of the pupil detection means is not limited to the one inFIG. 44, and this embodiment is also applicable to the positions inFIGS. 45 and 46.

(Embodiment 18)

FIGS. 49 and 50 are model drawings showing an eighteenth embodiment ofthis invention. FIG. 49 is a top view, and FIG. 50 is a side view. Theinternal structure of the virtual image forming optical system 3 and thedevice main body 1 are the same as in the above embodiment, so theycarry the same reference numerals, and their description is thusomitted.

The device main body 1 engages the holding section 43 via a hingesection 118, and the angle between the device main body 1 and theholding section 43 can be varied via the hinge section 118. That is, theinclination of the virtual image forming optical system 3 relative tothe user's eye 12 can be corrected. In this embodiment, any of theconstitutions of Embodiments 14 to 17 can be used to inform the user ofmisalignment caused by the inclination of the virtual image formingoptical system 3.

The user 2 may adjust the inclination of the device main body 1, inparticular, the virtual image forming optical system 3, via the hingesection 118 until the alarm from the means for informing the user ofmisalignment is cleared.

As described above, the inclination of the virtual image forming opticalsystem 3 can be corrected accurately and easily based on the position ofthe pupil determined by the pupil detection sensor 111. As a result, theuser 2 is prevented from moving his or her eyeballs unnaturally, so thefatigue of the eyes caused by the misalignment of the user's pupil withthe device is avoided, and the structure of the associated adjustmentmechanisms is simplified.

The hinge section 118 can be folded toward the holding section 43 tosave space.

Although the construction for correcting the inclination can be usedindependently, using this constitution with the above Embodiments (FIGS.44 to 48) enables both the horizontal position and the inclination to beadjusted accurately and easily, thereby minimizing the resultantfatigue.

In this case, the same pupil detection means can be used.

(Embodiment 19)

FIGS. 51 to 54 are model drawings showing an embodiment in which thehead-mounted display device according to this invention is used with akeyboard. The optical system in a monitor section comprises the imagedisplay element 9 consisting of the liquid crystal panel 7 and the backlight 8, an enlarging lens 121, a partially transparent mirror 122 therear surface of which is a reflection surface, and a full reflectionmirror 123 the front surface of which is a reflection surface, as shownin FIG. 51. The full reflection mirror 123 can be arbitrarily switchedbetween its closed state in FIG. 51 and its open state in FIG. 52. Inthe open state of the full reflection mirror 123 shown in FIG. 52, animage formed by the liquid crystal panel 7 is reflected by the rearsurface of the partially transparent mirror 122, and enters theobserving eye 12, while simultaneously an image of an external sightsuch as a keyboard also enters the observing eye 12. In the closed stateof the full reflection mirror 123 shown in FIG. 51, that light of animage formed by the liquid crystal panel 7 which has penetrated thepartially transparent mirror 122 is reflected by the surface of the fullreflection mirror 123 and enters the partially transparent mirror 122.The reflection surfaces of the partially transparent mirror 122 and thefull reflection mirror 123, however, adhere to each other, so that lightbecomes a double image, which never enters the observing eye 12. In thiscase, only the image light formed by the liquid panel 7 enters theobserving eye 12 with little loss. As shown in can move along a ssection 130 can move along a slide groove section 125 in a frame 124.The monitor section 130 is attached to the frame 124 by the tighteningof a fixing screw 126, and fixed by a fixing control 127. Signals andpower are supplied to the monitor section 130 via a cable 128.

Before starting an operation, the operator can view an image formed bythe liquid crystal panel 7 and an overlapping image of objects aroundthe operator including the keyboard, with the full reflection mirror 123set in the open state as shown in FIG. 52. In this state, the visualdistances between the operator's eye and the virtual image and betweenthe eye and the keyboard can be adjusted accurately by moving the liquidcrystal panel 7 in the direction of the optical axis to vary the lengthof the optical path in order to adjust the diopter between the image andthe keyboard. Furthermore, since the monitor section 130 can be movedalong the slide groove section 125 in the frame 124 as shown in FIG. 53,the selection of the eye over which the monitor section will be placed,the provision of appropriate settings for the visual line, and thearrangement of the positions of the image and the keyboard can becarried out flexibly and accurately. The operator subsequently switchesto the full reflection mirror 123 to its closed state to start anoperation. This saves the operator focusing for his or her eye which maybe required due to the difference between the visual distances to theimage and to the keyboard when the operator's glance is switched betweenthe image and the keyboard, thereby significantly increasing workingefficiency to substantially reduce his or her fatigue. Although in thisembodiment, the full reflection mirror 123 can be opened and closedusing one end of it as a support point, the same effect can be producedwith a detachable structure.

(Embodiment 20)

FIGS. 55 to 57 are model drawings showing another embodiment in whichthe head-mounted display device according to this invention is used witha keyboard. The optical system in a monitor section comprises the imagedisplay element 9 consisting of the liquid crystal panel 7 and the backlight 8, the enlarging lens 121, and the full reflection mirror 123 thefront surface of which is a reflection surface, as shown in FIG. 55. Themonitor section 130 in FIG. 56 is fixed to an observation window 127 viaa hinge, and the observation window 127 is rotatably mounted along theslide groove section 125 in the frame 124. The mounting structure is thesame as in the above embodiment (FIG. 54), and its figure anddescription are thus omitted. The opening of the observation window 127is the same size as the external shape of the screen of the monitorsection, and the position of the observation window 127 is set so thatthe cross section of the field of view used when the virtual image isviewed aligns with the opening of the observation window 127.

Before staring an operation, the operator springs up the monitor section130 so that it rests above the field of view, and moves the observationwindow 127 along the slide groove section 125 while viewing the externalsight through the observation window 127, thereby selecting the eye overwhich the monitor section will be placed, adjusting the visual line, andarranging the positions 129 of the image and the keyboard 128. Themonitor section 130 is then lowered and fixed. This enables thepositions of the image and the keyboard to be determined flexibly andaccurately, thereby preventing the two-dimensional overlapping of theimage and the keyboard to improve working efficiency and to reduce theuser's fatigue.

(Embodiment 21)

FIGS. 58 to 60 are model drawings showing another embodiment in whichthe head-mounted display device according to this invention is used witha keyboard. The optical system in the monitor section is the same as inthe embodiment in FIGS. 55 to 57, and its figure and description arethus omitted. As shown in FIGS. 58 and 59, the observation window 127and the monitor section 130 are detachably attached to a fixed claw 131movably disposed along the slide groove section 125 of the frame 124.The fixing structure is the same as in the above embodiment (FIG. 54),and its figure and description are thus omitted. The opening of theobservation window 127 is the same size as the external shape of thescreen of the monitor section, and the position of the observationwindow 127 is set so that the cross section of the field of view usedwhen the virtual image is viewed aligns with the opening of theobservation window 127.

As shown in FIG. 58, the operator attaches the observation window 127 tothe fixing claw 131 that can be moved along the slide groove section125, and moves the window 127 while viewing relevant objects through itin order to select the eye over which the monitor section will beplaced, to adjust the visual line, and to determine the positions of theimage and the keyboard. The operator then removes the observation window127, and attaches and fixes the monitor section 130 to the positiondetermined using the observation window 127 as shown in FIG. 59. Thisenables the positions of the image and the keyboard to be determinedflexibly and accurately, thereby preventing the two-dimensionaloverlapping of the image and the keyboard to improve working efficiencyand to reduce the user's fatigue.

The shape of the opening of the observation window is not limited to theone in this embodiment, and this invention is applicable to a roundopening 132 or a crossed opening 133 formed in the observation window127 of a transparent material with a cross section marked on the centerthereof in order to enable more accurate settings for the image, asshown in FIG. 60.

(Embodiment 22)

There have been some reports on VDT operators' postures duringoperation. One example is from Nikkei Electronics, 1984.1.2, p. 158.Based on this report and the inventor's measured values, it can be saidthat the average distance from the operator's eyes to an inputtingkeyboard is 60 cm.

VDT operators do not necessarily assumes such a posture. The inventorrandomly selected 20 VDT operators, and measured their postures duringoperation. Thirteen operators assumed a posture similar to thatindicated in the above report, while other four preferred almost fullystretching their arms. Four of those who assumed the reported postureperiodically stretched their arms during long time VDT operations. Thisis probably due to the operators' preference and intention to relaxtheir bodies by changing their postures. The distance from theseoperators to the inputting keyboard was about 80 to 100 cm.

Three operators wore nearsight spectacles and took them off during VDToperation. They were closer to the inputting keyboard during operation.

This is, of course, due to their intention to view the keyboard moreclearly. The distance from these operators to the inputting keyboard was40 to 50 cm.

Nine operators wore nearsight spectacles, and the three of them who tookthem off during operation had an eyesight of 0.3 or higher. Other sixoperators had an eyesight of lower than 0.3, and wore their spectacleson during VDT operation.

It can thus be said that many of those nearsighted people who take offtheir spectacles during VDT operation have an eyesight of 0.3 or higher.The eyesight of 0.3 corresponds to a spectacle diopter of about -2D,which further corresponds to the distance of 40 to 50 cm between theeyes and the keyboard.

Based on the results of these measurements, the inventor constructed avirtual image forming mechanism for the head-mounted display deviceaccording to this invention. This mechanism is described with referenceto FIGS. 61, 62A, and 62B.

FIG. 61 shows the arrangement of the components of this embodiment. Theliquid crystal pale 7 is fixed to the inside of the frame 76 including arack section, and the gear 77 that engages the frame 76 is disposed inthe rack section. Light output from the liquid crystal panel 7 isreflected by the mirror 10, enlarged by the lens 11, and then enters theoperator's eye 12. These components are all housed in the housing case140. This configuration is the same as in the above embodiments.

FIGS. 62A and 62B are sketch drawings of the housing case 107 in FIG.61. FIG. 62A is a side view, and FIG. 62B is a view seen from theoperator. The housing case 140 includes on its side the diopteradjustment control 78 connected to the gear 77 in FIG. 61 via the screw79 through a hole provided in the housing case. The tip of the diopteradjustment control contacts a guide 142 integrally molded in the housingcase 140 and having notches 141, and is frictionally retained by theelasticity the diopter adjustment control 78.

By moving the diopter adjustment control 78 along the guide 142 in thedirection shown by arrow 143, the operator can rotate the gear 77 inFIG. 61 to accordingly vary the optical distance between the liquidcrystal panel 7 and the lens in order to adjust the diopter.

An image formation distance 144 corresponding to the optical distancebetween the liquid crystal panel 7 and the lens 11 is displayed on theguide 142, so the operator can set an virtual image at an imageformation distance most suitable for his or her VDT operation.

Although this embodiment has been described in conjunction with thelever type diopter adjustment control, this invention is not limited tothis aspect, but is applicable to, for example, a dial type diopteradjustment control.

In this embodiment, the image formation distance was set 100 cm atmaximum and 50 cm at minimum. This setting can reduce the range ofsetting errors in the image formation distance as well as the size ofthe diopter adjustment mechanism.

The notches 141 are positioned so as to correspond to the imageformation distances of 50, 60, 100 cm. The results of the abovemeasurements indicate that in many cases, the virtual image ispreferably formed at such distances, and fixing the diopter adjustmentcontrol so as to correspond to these distances usually enables theoperator to adjust the diopter quickly. In addition, even when theoperator has changed his or her posture, he or she can adjust thediopter adequately with the head-mounted liquid crystal display deviceon using the positions of the notches 141 as references.

When this head-mounted liquid crystal display device is used, the imageformation distance is set at 60 cm if the operator assumes the reportednormal VDT operation posture. It is set at 100 cm if the operatorstretches their arms during operation, while it is set at 50 cm if theoperator usually wears spectacles and takes them off during operation.These settings substantially eliminate the need to vary settings for theliquid crystal when the operator switches his or her line of sightbetween the inputting keyboard and the enlarged image, therebysignificantly reducing the user's fatigue.

To confirm the effects of this invention, the inventor had someoperators perform VDT operations using the head-mounted liquid crystaldisplay device according to this invention, a conventional head-mountedliquid crystal display device, and a conventional CRT monitor to comparethe results. The results are shown in Table 3. The same 20 operatorseach performed each VDT operation for one hour. In this table, the errorindicates the value of the largest error in diopter in each operation,and the number of operators who had a sense of fatigue denotes thenumber of operators who sensed a fatigue of the eyes after theoperation.

                  TABLE 3                                                         ______________________________________                                                              Head-mounted                                                                              Conventional                                                      display device                                                                            head-mounted                                                      according to                                                                              display                                     Evaluation item                                                                             CRT     this invention                                                                            device                                      ______________________________________                                        Error in diopter                                                                            0.2D    0.3D        1.2D                                        Number of     3       5           16                                          operators who had                                                             sense of fatigue                                                              ______________________________________                                    

As is apparent from the table 3, when the head-mounted liquid crystaldisplay device according to this invention was used, the differencebetween the diopter for the inputting keyboard and the diopter for theenlarged virtual image is significantly small and generally similar tothat for the CRT monitor. The difference, however, is relatively largefor the conventional head-mounted liquid crystal display device.

The operators' fatigue from the head-mounted liquid crystal displaydevice according to this invention is similar to that from the CRTmonitor, and clearly much smaller than from the conventionalhead-mounted liquid crystal display device.

What is claimed is:
 1. A head-mounted display device comprising avirtual image forming optical system including an image display elementand an enlarging optical means for enlarging an image formed by saidimage display element as a virtual image; a device main body that housessaid image forming optical system; and a switching means mounted in saiddevice main body for holding said virtual image forming optical systemin such a way that the system can be moved in the direction of the widthof user's eyes and placing said virtual image forming optical system infront of one of the user's eyes, wherein:said image display element andsaid enlarging optical means are disposed so that the optical axis ofsaid virtual image forming optical system approximately aligns with theuser's line of sight taken while he or she is looking horizontally.
 2. Ahead-mounted display device according to claim 1 wherein said switchingmeans comprises a shaft that is retained so as to rotate withoutaffecting said device main body, that extends approximately in thedirection of the width of the user's eyes, that is shaped like a screw,and that has said virtual image forming optical system spirally fittedthereto.
 3. A head-mounted display device according to claim 1 furtherhaving a partially transparent shading plate provided in front of theeye that need not see an image enlarged by said enlarging optical meansand having a transmittance of less than
 1. 4. A head-mounted displaydevice according to claim 3 further having a control means for variablycontrolling the transmittance of said partially transparent shadingplate according to the surrounding illuminance.
 5. A head-mounteddisplay device according to claim 4 wherein the transmittance of saidpartially transparent shading plate is controlled so as to be 3% orless.
 6. A head-mounted display device according to claim 4 wherein thetransmittance of said partially transparent shading plate is controlledso as to increase when the surrounding illuminance is 1001× or less. 7.A head-mounted display device according to claim 3 further having apartially transparent shading plate with a transmittance of less than 1which is provided in a space opposite to the user relative to saidvirtual image forming optical system to cover at least the overallmovement area of said virtual image forming optical system.
 8. Ahead-mounted display device according to claim 1 further having acontrol means for variably controlling the brightness of said virtualimage forming optical system based on the surrounding brightness undersaid device main body and near the user's hands while the device is inuse.
 9. A head-mounted display device according to claim 8 wherein thebrightness of said virtual image forming optical system is controlled soas to be equal to said surrounding brightness.
 10. A head-mounteddisplay device according to claim 8 wherein the brightness of saidvirtual image forming optical system is controlled so as to beapproximately in proportion to said surrounding brightness.
 11. Ahead-mounted display device according to claim 1 further having adiopter adjustment means for adjusting the position in which an enlargedvirtual image from said image display element is formed.
 12. Ahead-mounted display device according to claim 11 wherein said diopteradjustment means further has a diopter adjustment control provided onboth sides of said virtual image forming optical system.
 13. Ahead-mounted display device according to claim 11 wherein the conditionsof said diopter adjustment means are shown so as to correspond to theposition in which said virtual image is formed.
 14. A head-mounteddisplay device according to claim 11 wherein the position in which saidenlarged virtual image is formed can be set stepwise at one of aplurality of positions using said diopter adjustment means.
 15. Ahead-mounted display device according to claim 1 further having aholding means attached to said device main body via a rotatable hingesection for holding said device main body to the user's head.
 16. Ahead-mounted display device according to claim 1 further having a drivecircuit fixed and disposed outside the movement space in the transversemovement area of said virtual image forming optical system for drivingsaid image display element; and a flexible printed circuit interposedbetween said image display element and said drive circuit for connectingthem together.
 17. A head-mounted display device according to claim 16wherein said drive circuit has a detachable part disposed approximatelyin parallel with the direction of the width of the user's eyes forallowing said flexible printed circuit to be attached to or removed fromsaid drive circuit in the direction that aligns with the lateral movingdirection of said virtual image forming optical system, and further hasa guide means disposed between said detachable part and said imagedisplay element for guiding said flexible printed circuit approximatelyperpendicular to the lateral moving direction of said virtual formingoptical system.
 18. A head-mounted display device according to claim 1further having a center determination support means provided in theapproximate center of said device main body and used to determinewhether or not the user's center line aligns with the center of thedevice main body while the device is in use.
 19. A head-mounted displaydevice according to claim 1 further having an antidominant eyedetermination support means provided in the approximate center of saiddevice main body and used to determine the antidominant eye.
 20. Ahead-mounted display device according to claim 1 wherein said virtualimage forming optical system has a partially transparent mirror andfurther has a pupil detection means disposed in the positioncorresponding to the optical axis of said optical system for detectingthe position of the user's pupil via said partially transparent mirror,and a means for informing the user of the misalignment of said virtualimage forming optical system with the pupil in response to the output ofsaid pupil detection means.